Hello,
Since you updated the device with ‘keep settings’ enabled, could you please try resetting the device to factory defaults in System → Maintenance → Backup? The configurations will be lost, so you will need to reconfigure the device again. It is possible that there were issues migrating your configurations to newer firmware.
Also, did you have IPSec configured on the older firmware? If so, were you able to access the WebUI then?
Kind Regards,