This message " This Access Point is not approved/joined yet. Please connect it to proceed configuration", appears in 2 cases:
1. AP isn't yet approved (automatically or manually).
2. AP was approved, but it has not yet completed configuration cycle. Usually new AP reboots 4 times before it is ready - main and backup software upgrades to current version, country setting change, mesh mode change -- and it takes some time. If AP have been connected to the same ZD previously, just was deleted, connection happens much faster -- AP already has proper SW, proper country setting, probably even proper mesh mode - so it may be provisioned immedietly.
Anyway, you must see messages about this AP progress in the lower part of AP Monitoring page.
By the way, if you have not enough AP licenses, than you'll see in the log that AP joining was denied because of no free licenses.
Hope it helps,