I can confirm this problem. It doesn't always happen after the first Opera close. Sometime it takes few times to close and reopen Opera. Then pinned tabs become unpinned. It think it is not Linux specific thing. I can see similar topic in Opera for Windows subforum: https://forums.opera.com/topic/35882/tabs-are-not-pinned-after-i-close-opera

Now it works! That means that changing password helped in my case.

Same problem here. "Something went wrong" after ~30 seconds. It had broke after Opera update with adding password sync (I have switched it on then and I am not able to switch it off now).

EDIT:
After changing password on https://auth.opera.com/account/edit-profile and resetting passphrase in Opera setting it is displaying "Connection to synchronization server is temporarily unavailable.".
This might be a progress actually. I'll wait and check if it will start working soon.