I doubt uninstalling removes any saved variables or user settings. I’d be surprised if it did. If that’s the case, re-installing wouldn’t fix anything. You’d have to manually find those files yourself and delete them.
Are you on PC? Do you use any addons? Have you checked the settings on the chat tab (right-click chat tab to find them) and made sure group and guild chats are selected?

I've already submitted ticket after ticket and still have the same problem. PSN chat works great.
Update, so at 7:50pm Eastern time, I disconnected my PS4, the HDMI cord and disconnected my router and modem till 9:15pm.
Chat worked again. I shut it down till tomorrow.
Will see.

The only thing I want to understand, is ESO fixing the Guild & Group Chat

Have a screenshot of the ticket #.
So, the last time I commented on this worthless Guild Chat and Group Chat problem, I unplugged my PS4 and it worked.
Problem is, if this is what I have to do everytime
it doesn't work, especially when starting a trial,
can you imagine the rest of the other group members having to wait for me to unplug my PS4
so I can be heard 😂🤣🤣😂🤣😂🤣 yeah right,
I'll miss a 1/4 on the trial.
It happened again last week. I was heard in Group Chat but, unable to get in Guild Chat.
Unplugged in console and could be heard again. 🙄
PSN chat is the way to go. No problems, no, can't be heard during a loading screen. It's a relief.😁