What apps are these? Due to certain old certificates expiring at the beginning of the month, Any apps that rely on this old certificate (and can’t be updated) will not be able to securely connect to your plex server. See if your device falls within this page. It also provides steps you can do to resume connecting to your server on those older device apps.
Edit: Seems some people having issue with certs (mostly for RASPLEX) have had success asking for their cert to be reset in this forum post. It’s above me, I don’t see how the issue I described could be “fixed” on Plex’s side by resetting a cert, but I’m sure I just don’t know enough about certs. Maybe try asking there.
