BIGIP 4000 stuck without config after upgrade to 14.1

Hi all, we're building a new infrastructure using two existing, licensed and supported F5 4000Ss with APM. We had everything up and running and the devices in a configsync pair. As the final cherry on top I decided to upgrade from 13.1.0.7 to 14.1.0 as it seems to have some cool features. Install went fine, I saved the config (from the first device only, stupidly), swapped the active partition, copied config and rebooted the standby box and it won't load a config (I get "The configuration has not yet loaded. If this message persists, it may indicate a configuration problem."). I tried returning to the original partition (without copying config from the 14.1 boot) and get the same problem. I then found K7727 which reports the licence activation date is important. Tried reactivating and then both 13.1 and 14.0 boots, but no joy.

 

Worst case, I figured I'd just wipe the unit and set up configsync again, learning my lesson for not saving the standby config! Problem is, I can't configure anything, nor get to the CLI, as the admin user has the console disabled, nor can I change the user config (I get "An error has occurred while trying to process your request." when I click on the user).

 

The active unit is OK and working (and I'm not touching it!)

 

Any help much appreciated as I'm a little stuck...

 

Many thanks, Corin.