ZeroTier Integration - Routing Issue

Hello Folks,
i’ve just received my new Slate Plus GL-A1300 router and so i started as first thing to update it.
Now i’m on latest firmware (4.2.1) and the ZeroTier integration is not working as it should…

Here below the complete setup, to allow you to bettere understand what is not working and, if you can, help me to find a solution to my issue:

As you can see, routing is hanled all via static routes in both Fortigate firewall and ZeroTier cloud, every network object is able to reach every destination always.

The only issue i have is to reach network 192.168.8.0/24 network, except for 192.168.8.1 router address (RemoteLan) form every ZeroTier source and from Home LAN too.

“Allow Remote Access LAN” is enabled, whats more from “LuCi” interface in “Firewall”
section traffic is allowed.

If i try to reach a device in 192.168.8.0/24 network from any other network the resoult is packet loss

source: 10.60.1.25

C:\Users\Administrator>tracert -d 192.168.8.198

Traccia instradamento verso 192.168.8.198 su un massimo di 30 punti di passaggio

  1    <1 ms    <1 ms    <1 ms  10.60.1.1
  2     1 ms    <1 ms    <1 ms  10.60.6.2
  3   171 ms    26 ms    28 ms  10.70.0.15
  4  10.70.0.15  rapporti: Protocollo di destinazione non raggiungibile.

Traccia completata.

C:\Users\Administrator>

Same story if i try to reach 10.60.1.0/24 or 10.70.0.0/24 network from 192.168.8.0/24 network, but if i try to SSH into the Slate Plus and perform pings and curl form inside the OS, the story changes:
i’m in fact able to talk back to any network device reached by ZeroTier:

root@GL-A1300:~# ping 10.60.1.25
PING 10.60.1.25 (10.60.1.25): 56 data bytes
64 bytes from 10.60.1.25: seq=0 ttl=126 time=24.555 ms
64 bytes from 10.60.1.25: seq=1 ttl=126 time=26.950 ms
64 bytes from 10.60.1.25: seq=2 ttl=126 time=63.414 ms
64 bytes from 10.60.1.25: seq=3 ttl=126 time=23.399 ms
^C
--- 10.60.1.25 ping statistics ---
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 23.399/34.579/63.414 ms

even if i use 192.168.8.1 as source

root@GL-A1300:~# ping 10.60.6.2 -I 192.168.8.1
PING 10.60.6.2 (10.60.6.2) from 192.168.8.1: 56 data bytes
64 bytes from 10.60.6.2: seq=0 ttl=64 time=22.245 ms
64 bytes from 10.60.6.2: seq=1 ttl=64 time=26.110 ms
64 bytes from 10.60.6.2: seq=2 ttl=64 time=30.480 ms
64 bytes from 10.60.6.2: seq=3 ttl=64 time=24.124 ms
^C
--- 10.60.6.2 ping statistics ---
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 22.245/25.739/30.480 ms

Guys, do you have any clue why this is happening?

Many thanks in advance for your time!

Feel free to ask anything else about my setup!