Almost guarantee as you are running it on Windows 10 - when you first establish the Zerotier connection (the first time and enable it on the ZT network - the Windows PC will pop up and ask you "do you want this PC to be discoverable by other devices on the network" - if you do not see this or do not answer in time - it disappears and then categorises the network as a Public not private network - and then lots of firewall things come in place.
So two things - go into network and internet settings and check what the network is classified as
If it is a public network - then this will probably be your problem - if you antivirus software also incorporates a firewall which takes over from Windows firewall then it will be even tricikier.
If you are just using windows firewall and see the network listed as public then you can use this powershell script
Try if after going through those steps.
After that then check if you have a firewall with your antivirus software and try and change the ZT network to private in there also
Craig
