Hey guys sorry for late update....
I still didn't fix my issue....like I say before I am not a PRO so I really need a step by step help if someone has time.

The main issue is that the two site can't ping each other but I can from the laptop and access to both network LAN clients.

I tried to create a new GATEWAY and select the Zerotier interface + made a static rule but is not working.

@scottalanmiller Hi, I try it but is not working.

@Pete-S Hi, I followed the instruction already, I have already done it.

@Dashrender Yes I need a "Site to Site" VPN, but because I don't have a static or public IP, I can't use something OpenVPN.

Hi everyone....
Hope you guys doing well over this crazy time

I have two office and a laptop that need to be connected together by using ZeroTier over the internet.
Each site has a 4G internet connection without public IP.

I installed of each OPNSense router the ZeroTier client and assigned to the ZT interface a static IP.
On the laptop (Linux Mint) I successfully install the ZeroTier application and registered to the network

Below you can see details

SITE 1
OPNS IP: 192.168.2.1/24
ZT INTERFACE: 10.10.10.2
WAN: 4G

SITE 2
OPNS IP: 192.168.3.1/24
ZT INTERFACE: 10.10.10.3
WAN: 4G

LAPTOP
ZT INTERFACE: 10.10.10.4
WAN: 4G

At this stage I can only ping and access the local network just from the laptop to office 1 & 2 by using the local network ip address but
I can't ping office 2 from office 1 and vice-versa.
I think I need set some rules on the OPNSense router but I am not sure how to do it.

Any one can please help me with this?
Thanks a lot