10-29-2018 04:49 PM
I have just updated Unifi Controller from a very old version to current and along the way had a lot of trouble with lost sign-in credentials. (I've never been able to get Unifi Controller and gmail to communicate via SMTP which is required for password recovery.) The key to success is to use incremental updates to avoid too large a jump between versions. Ubiquiti help desk advised the following sequence 2.4.6 > 3.2.10 > 4.8.20 > 5.6.39 > 5.9.29 (latest stable). All system settings etc survived the update process. After each version was up and running and settled down, I made any AP firmware updates that were indicated although I understand that could have been done once at the end.