Readarr's metadata server is responding with rate limiting (HTTP 429) frequently because of the downtime and everyone's systems hitting it to get list imports, etc. This is expected to slow things down for a week or few until everything is running like normal again. If you're trying to import, or search, etc. and those things are slow or failing, your logs will indicate a 429 error. This will get better. Please have some patience and it will resolve in time.
Search is coming back online.
The current state of the Readarr metadata server:
Searching is currently down. I will advise when it's back up. This will impact adding new authors, books, and manual imports where searches are required to function.
There was a change in Calibre 7.2.0 which starts listening on ipv6, and it can cause a problem with readarr connections. To fix it, change the setting "The interface to listen for connections" to 0.0.0.0 in Preferences->Sharing over the net->Advanced, in calibre, and restart calibre. This should resolve the issue.