Goto the URL opera://settings/content/siteData, make sure the default behavior is set to "Allow sites to save data on your device" and make sure all the customized behavior lists are empty. Then, goto the URL opera://settings/cookies, make sure it's set to "Allow third-party cookies" and make sure the allow list is empty.

Then, goto the URL opera://settings/content/all, type google.com in the search field and click "Delete displayed data".

Then, goto the URL opera://settings/clearBrowserData and clear "Cached images and files" for all time.

Then log in to Google and try things. If things work fine, restart Opera and make sure they still work fine. If not, there are other things we can try.