Can someone please help with the following:

Since I updated Plex on my Xbox one a few days ago, my Xbox won’t connect to plex anymore…strangely my iPhone, laptop, PC still works fine…any ideas of how I can fix ( I’ve restarted both my plex server and Xbox one - no change )

That’s not a lot of information to go on. But things I would suggest doing would include trying it on other clients to make sure it’s the client and not your server as well as you can try reinstalling the client.

strangely my iPhone, laptop, PC still works fine…

Yeah, he says he’s already tried other clients and they are still having issues…

Couple of things to try, not sure if they will work or not, since I don’t own any gaming consoles myself…

Open the Plex app on the Xbox and then sign out and sign back in. Usually this works with other clients. Try powering off the Xbox completely by removing the power cord and counting to 10 then plug it back in.

Report back so we know if this worked for you. You can also try checking the Xbox forums here to see if others are reporting the same type of thing…

Does it give you the cannot connect to server message?

If so you might be affected by the secure connection issue talked about in this thread:
https://forums.plex.tv/discussion/196676/plex-for-xbox-one-unable-to-connect-to-server-1-3-1