ZeroTier Reconnection

I have an issue that hopefully someone can help / clarify. I have zerotier running on an odroid which in turn runs the home automation system in a property that is a many hours drive away. My electrician needed to do some work in the property and therefore turned off various circuits and disconnected my internet router. Once he had finished, he turned the odroid back on and just before he left, he remembered that he had not turned on the router, so turned it on and left.
So, my odroid is now connected to the internet (I can access openHAB), but on zerotier comes up as offline. It has now been a few hours. I assume that when the odroid booted up, as the internet was down with the router being turned off, zerotier timed out. I was hoping that zerotier will periodically check if the internet is up and reconnect itself? Perhaps I am mistaken, and the only way is to reboot the odroid, which means that my electrician needs to make another trip to the property? I had checked previously that zerotier comes up automatically on boot.
Thank you.