List of connected devices doesn't appear anymore !!

You surely should backup your config, before performing a factory reset, but it could very well be - just as Darren noted, that the settings of your device(s) have been screwed up. In that case restoring your current config would surely re-introduce your issue.

However, it may be worth a try to factory reset and then restore your config… The question is, if your issue is actually caused by a config issue, or some other problem and if your issue is caused by a config issue, will the backup include this error. No other way to find out, then to try, I guess.