You might have setup a new Ubiqiti access point using a controller based at another site, which is not the final destination of the device, so it is no longer configurable when you get to the new site.

If you can get the Old controller back up and connect to the access points you can use the below to move the Access Points to a new site via the Site Migration

https://help.ubnt.com/hc/en-us/articles/115002869188-UniFi-Migrating-Sites-with-Site-Export-Wizard 

If you cannot connect to the old controller anymore you can try logging into the access point via IP and doing:

You can use the Same Old Controller name : 

1. SSH into AP with former controller’s credentials
2. in controller, forget AP
3. reset to default with ‘syswrapper.sh restor-default’
   connection will be terminated
4. SSH into AP with ubnt/ubnt
5. use mca-cli shell
6. set-inform x.x.x.x:8080/inform
7. where x.x.x.x is the ip of the new unifi controller
8. in controller, adopt the AP
9. repeat step 7 after adoption (sometimes this is necessary to get to provisioning)
10. AP will reboot and provision

Finally you can perform a factory reset on the device to join it to a new controller

https://help.ubnt.com/hc/en-us/articles/205143490-UniFi-How-to-Reset-the-UniFi-Access-Point-to-Factory-Defaults