BGP over RBVPN AS PREPEND

Good morning everyone,
I configured the BGP over RBVPN between our office and the 2 connectivity present at one of our customers (fiber and radio link), the connection is made via the prepend AS also tried with LOCAL PREF AND MED, if I try to switch off the fiber link neighbor, the traffic passes on the radio link , I can ping the firewall and can telnet on firewall but I cannot  reach it via the GUI, if I reactivate the main link the ping also works correctly but in this way  I can reach the sophos gui, can you help me solve the gui reachability problem via the backup link?
Thanks

Our firewall is SFVUNL (SFOS 19.0.1 MR-1-Build365)
Customer firewall: XG125 (SFOS 19.0.1 MR-1-Build365)

Thanks

Valerio



Edited TAGs
[edited by: emmosophos at 7:13 PM (GMT -8) on 30 Nov 2022]