I had the opposite problem - couldn’t get it to disarm. Total shot in the dark here, but if you are using phones and/or presence sensors to change arming status, here’s what worked for me, and might possibly help you:
I don’t know if this will apply to many people, but here’s my experience…
Yesterday for the first time during the ongoing outage, I experienced a SHM failure. It wouldn’t disarm and kept setting off alarms. I opened a ticket, and as a workaround in the meantime, removed all sensors from SHM configuration (so it no longer mattered that it didn’t disarm). Today I noticed that the house was also stuck in Home mode when no one was there. Attempting to manually switch mode via smartapp or Goodbye routine had no effect. Then I remembered that I had a virtual presence sensor as part of my “when someone arrives” scenario, that is used only for testing. I hadn’t touched it in weeks. Once I toggled its state, everything started working normally. That is, SHM disarmed, and when I manually toggled Go…