FAP321C upgrade to 5.4.0 issues

[cardinal]

Upgraded one of my  FortiAP (FAP321C) to version 5.4.0, now the the web interface is no longer avaliable.  I'm loathed to upgrade the other one just in case I lose web connectivity to it as well.

I have gone throught the manual and there is very little in there that is helpful.

Has anyone come across this issue and if so how was it fixed

Cheers

[Amanuel]

Login to the fortigate with a console and set the management IP address via CLI, then login to the Fortigate via the Management IP address.  you should not loose any other config except the Interfaces configuration. My self i noticed more config losses with HA, SSL VPN Portal customization and AD integration.