I have two Rachio Gen 2s that have been in service for years. One was offline today, flashing light #2 and I fixed it by cycling power to the Rachio (the router was not touched)
It is very inconvenient to physically access the Rachio at this location, so here is a suggestion:
Your firmware could/should recognize that it is “stuck” and, after some period of time (30 minutes? 1 hour), reboot itself and try again. Seems like no harm could come from this and there are plenty of cases where this would rectify a connection problem.