@lailaamell My primary is Brave and no issues for a good while. Both Brave and uBO are up to date. I don't use any other security extensions or ad blockers. My secondary is Opera and I just test it earlier and on YT, it seemed to be working just fine.
I am not saying you are wrong but either what I mentioned before is the cause or there might be other variable(s). I think each user needs to do some testing to narrow down the variables to figure out the culprit.
Also see this test I did less than a year ago: https://www.youtube.com/watch?v=CHrLIJloojA

@MultiSingularity said in uBlock Origin:

@turcoloco I apologize, I wasn't clear enough. You uninstall ublock origin, not opera. My bad for my lack of clarity.

Oh, no worries. Yes, with uBlock Origin, I had to do that once in a long while even though the auto update was selected. You could tell this is the problem when all of a sudden ads would no longer be blocked on YouTube.

@MultiSingularity said in uBlock Origin:

@kacperopera: Uninstall it, clear cache and cookies, restart opera, reinstall. It fixes it, at least temporarily. Needed to do it again about a week later, but worth it honestly.

You shouldn't have to uninstall a browser unless you are having error when launching the browser or when trying to update it.

Just about all browser data that matters will be in the %AppData% and %LocalAppData% folders. Some use just the \AppData\Local\ (ie. MSEdge, Chrome, Brave) and some browsers use both the \AppData\Local\ and \AppData\Roaming\ folders (Opera, Firefox, Waterfox).
Browser folder under \Local folder typically contains static data and maybe the session data where \Roaming folder will have bulk of the data and most importantly, user, extensions and other profile specific data.

If a user is experience problems with their browser on a specific site, best to make sure their browser is up-to-date, then start a "private" aka "incognito" session which will effectively disable all extensions, cookies and dynamic cache for that session. Check to see if the site is still having issues or not. If not, you know cache, cookies and/or extensions are likely the culprit. If still having issues, then more than likely a more complex issue inside the user browser profile to be the culprit.

If that is the case, I'd simply close the browser in question, then rename the browser folder to something that starts with OLD_. So, if using Opera browser, rename both "Opera Software" folder under \AppData\Local and \AppData\Roaming so they read:
"C:\Users\youruser\AppData\Local\OLD_Opera Software" and "C:\Users\youruser\AppData\Roaming\OLD_Opera Software"
Then fire up Opera and visit the site again to see if you still have the issue or not.

When you uninstall a browser, the browser's user data folder(s) under \AppData\ are not related. If renaming the folders didn't fix the issue, then uninstalling the browser from the system would make sense as well as hiding the existing data folders as mentioned above.

@kiquja Click on the UBO icon on the extension bar (assuming it is visible at the right top corner of the browser, then look for triple gear icon which is for settings. If the uBlock Origin icon is not visible then hold down the CTRL and SHIFT keys then press E on the keyboard. Then locate UBO on the extension list and then click on the Options under UBO. Go through the options under the "Settings" and the "Filters Lists" tabs.

Most importantly, keep uBlock Origin up to date. major browser update can break its auto update function especially is there is a major update to the browser and it is not compatible with the current version of uBO.

Another fact Opera users need to keep in mind is, unlike Brave or Firefox, most other mainstream browsers including Opera are using Chromium engine which no thanks to Google, has been slowly but surely getting pushed with Manifest V3 rules the last year so eventually uBO will not work right or at all with Chromium based browsers like Opera/Edge/Chrome/Vivaldi. What you need to do is, swap uBlock Origin with uBlock Origin Lite which is supported by Manifest V3. This version of uBlock is not quite as configurable or effective as the uBO but it will not likely to have any issues either.

My current primary browser is Brave and I am using uBlock Origin Lite and no issues on YouTube.

@taffercharles When a device driver is crashing, even if a browser or an extension may seem like the prime suspects, I assure you it is your device driver and possibly also your file system (Windows) that has issues. Quick fix would be to check to see if there is an update to your audio drivers. If there is, download and install it. If there isn't, uninstall the existing one from the Device Manager. Restart your computer before reinstalling the audio drivers.

It is always best to start doing the simplest and least destructive troubleshooting steps first.
So, for browser related issues, try another browser (I always have at least 3 for this reason).
Use a browser with a different engine if possible. Also make sure at least one of the browser do not have ANY extensions OR test YouTube running your choice of browser in "in cognito" (private) mode which opens a new session where all extensions are disabled and no static or dynamic data from the actual browser user profile is loaded. If that checks out OK then launch the browser in normal mode, make sure you have only the home/start page open then clear out all browser cache (CTRL+SHIFT+DEL) make sure to check everything except for maybe the logins/passwords/sign-in data also make sure the time range "All Time". Let it rip, once done, close the browser and re-open to check (YouTube, etc.). If the issue still persisted, then I would first Remove/Uninstall uBO. Then if there is an update to the browser, update it. Final step would be to re-install uBO. I'd not recommend having multiple security extensions installed on the same browser, especially multiple extensions to have the same function, that is never a wise move. Similar to running multiple AV products in real-time on the same machine. Just not a sound configuration and could cause issues or slow down the machine. Same with extension, less is more.

PS. When I still had AmazonPrime subscription and they started showing ads even in their own programs, uBO didn't help. What helped was Privacy Badger so, if all else failed, give Privacy Badger a shot.

@lailaamell My primary is Brave and no issues for a good while. Both Brave and uBO are up to date. I don't use any other security extensions or ad blockers. My secondary is Opera and I just test it earlier and on YT, it seemed to be working just fine.
I am not saying you are wrong but either what I mentioned before is the cause or there might be other variable(s). I think each user needs to do some testing to narrow down the variables to figure out the culprit.
Also see this test I did less than a year ago: https://www.youtube.com/watch?v=CHrLIJloojA

I have noticed uBO failed to block ads once or twice in the past, especially if I updated the browser a short while earlier. This seemed to have happened mostly when the extension failed to update itself even if it was set to auto update.

When this issue occurs, whether it is the latest version or an older version, best to remove the current extension and install the latest one instead of trying to get it to update.

@szczurwysyn Same as the update of uBO failing, try removing uBO and then re-installing the latest version. I had that issue when I was using Opera but still I believe the issue is between the browser and the add-on.

Inconsistent ad blocking on YouTube otherwise, great extension!