BIGIP 4000 stuck without config after upgrade to 14.1

Are you able to log in as root via SSH/Console?

if so it's an idea to check that the bigip config is there by typing "cat /config/bigip.conf"

If that appears to have your config then it's possible that the BIG-IP just won't load the config. If this is the case try "tmsh load sys config" and it will fail, but at least give you an error to say why it won't import the config.

Also, if you can't login as root via the console/SSH but have GUI access, you can enable admin's CLI access and/or review the LTM logs through the GUI to see why the config won't load.

HTH