This seems to be an error introduced with OH 3.3.
I have it as well, just as many others. Another thread with the issue is this one: Thread
For me, what usually works is:
- deactivating the deconz thing
- activating the 3rd party app pairing in the Phoscon Webinterface
- deleting the API key in the deconz thing
- activating the thing, it will generate a new key.