Gateway remain offline even if is back online

[ermannobonfazi]

 I have 2 gateway, one DSL (GW1) and one 4G (GW2) The first one have priority 1 and monitor IP 8.8.8.8, the second have priority 100 and monitor IP 8.8.4.4.  I if test failover manually disabling the main gateway GW1, than it switch to GW2 autotomatically and and re-enabling GW1 switch the active gateway to GW1 and all works.
If I physically disconnect the cable from GW1, than automatically switch correctly to GW2, but when I reconnect the cable, even if I can ping the gateway GW1 IP from any computer, in OPN the Main gateway GW1 remain OFFLINE, until I manually click again to enable manually. Any help?