Since the 6.1.8 update, my Plex shares have stopped working. I get the message “An error occurred. Sorry, Infuse encountered an error while trying to connect.” I was watching a movie and stopped to make dinner. I come back, see that there is an update for Infuse, install the update, then this message. It’s the same on iOS, too.
One quick thing you can try is to walk through the ‘Connect to Plex’ steps again in Infuse > Settings > Shares. This will update the credentials for the Plex connection, which often times can help resolve issues like this.