How to upgrade ZeroTier sw in GliNet routers

Hi all, I have 2 GliNet routers connected to 1 ZT Network. When I see the ZT Network in the website I see both are connected, and in the version 1 says 1.8.4 and the other 1.10.3
I have some and as part of the troubleshooting it was suggested to take them both to the latest SW release. Does anyone know how to upgrade them?

I have the same question although I have different versions running on the router and PC.