Hi Yuri,
Please check the following:
1. Is the clock on IAP showing the correct time?
#show clock
2. Is there a valid DNS server assigned to the IAP in order to resolve the Central URL ?
# ping google.com
If DNS is working, we should see the response from google.com
3. Is there a firewall on the network which could be blocking the HTTPS communication between IAp & outside network.
4. Please attach the following outputs:
#show version
#show aps
#show clock
#ping google.com
#show log provision
#show activate-status
#show ap debug cloud-server
# show log ap-debug | include awc