The only thing that immediately comes to mind is a possible server change like what happened with other Plugs last month:
In that case, Wyze had to make a back-end change and then the Plugs had to be power-cycled for the issue to resolve:
I’m just speculating, but I don’t have a better explanation at this point. If the Plug Outdoors aren’t coming back online at all, then I’d consider submitting a log for your locally-available Plug Outdoor the next time it goes offline and then following that up with a Support ticket so that Wyze Support knows to direct that log with relevant information to the appropriate engineers.
I think you’ve done good troubleshooting so far, and I appreciate your mention of no recent firmware updates (the last I see available are from March). The only other thing I might consider at this point is deleting the app, rebooting your phone, doing a fresh install of the app, and rebooting your phone again. I wouldn’t expect that to resolve anything, and I think it’s kind of a last-resort step on the user side. My bet on this one would be a server issue.