We run 2020.9.0.1, not any problems applying labels, but i get some kind of wierd warning after applying label saying that its in invalid status an needs to be cleared!

But after clearing that and reapplying the label it works as expected :)

Haven’t seen that yet.  Might try to reboot Prism Central again tomorrow.

Any clue in the logs?

I can see that this issue has been raised internally already. There is no workaround or conclusion on this yet as it is only a few days old. I’d suggest opening a support case. This would help with tracking the issue. Also, the issue that I see being logged may not be the same as yours as in it may look the same but have a different root cause.