The TV has a clock, or a time-and-date setting.
Go into the TV's MENU system, by pressing the MENU button on the remote.
See if you can set the clock, or the time-and-date, and make sure it has the right month and year in it.
Also check on your home page, or try to access a different page. The page you have programmed in to the TV, to access upon connecting, may be defunct, or no longer there, or otherwise extinct/unusable/obsolete.
(That is hinted at, by the "certificate expired" message. It signifies that, since certificates are issued for years, the page may be quite old.)
If any of this seems inobvious, needs more explanation, etc., let me know. I will try to guide you through it.