Error after update to version 13.2.9

Lately I updated to version 13.2.9 and now it permanently shows the following error:

“Here is an error associated with Connecting WP REST API
Please Flushing rewrite rules by updating permalink in?Settings->Permalinks?and make sure the WP REST API is enabled.”

I updated the Permalinks but it didn’t change anything.

Any ideas what could go wrong? Thank you!