Syncserver-rs does not work on Firefox for iOS

[giovi321]

I have installed syncserver-rs and it works excellently on an Ubuntu and a Windows 10 clients.
I tried to add my iOS device but it simply does not sync. It says "synchronized" and reports the last sync date but nothing shows up from the other devices, nor anything shows up on the other devices from the iOS device.
I configured the iOS device to point to the syncserver-rs:
"Use custom FxA Content Server": https://accounts.firefox.com/
"Use Custom Sync Token Server": https://mydomain.com/token/1.0/sync/1.5
Note that on both computers I used the address "https://mydomain.com/1.0/sync/1.5" and not "https://mydomain.com/token/1.0/sync/1.5" and it works great.
On Firefox for iOS:

• if I use "https://mydomain.com/1.0/sync/1.5" it says sync failed, and nothing syncs
• If I use "https://mydomain.com/token/1.0/sync/1.5" sync seems to work but nothing syncs anyway.

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