I have a similar issue (not sure I should create a new post or reply this one...) :
There is a RUT-240 with a valid zerotier access. Most of the RUT settings are default ones, except LAN and WAN ip addresses and admin password.
The RUT WAN port is linked to an internet provider ADSL router (the "box").
The RUT LAN is linked to a Bacnet controler "Eclypse".
The customer's PC has an internet access through his mobile phone 4G connection. Its zerotier ip address is 192.168.191.157
"box" Lan : 192.168.2.254/24
RUT Wan : 192.168.2.1/24
RUT Lan : 192.168.1.1/24
RUT zerotier : 192.168.191.33/24
"Eclypse" : 192.168.1.10/24
From the customer's PC, we can ping the RUT zerotier ip, but we can't ping the Eclypse. We have tried to disable the firewall, but it didn't help.