Try going to settings -> misc -> default server address and changing it to https://api.sponsor.ajay.app

In some countries such as Russia, they have blocked the main sponsorblock server

The latest version of "Enhancer for YouTube" causes issues with sponsorblock. You can downgrade that extension until they publish their fix.

https://old.reddit.com/r/SponsorBlock/comments/1gtl3f1/do_this_if_your_extension_has_stopped_working_on/