Basically there are three issue that always occur on hetzner server when virtualizor tries to create bridge :-
1)It cannot create a bridge due to missing Gateway .
You have to add GATEWAY= .
You can get the gateway from SCOPE=
2)If the network mask is 255.255.255.255 it will fail to create a bridge .
You have to change netmask to any other netmask then 255.255.255.255
3)You have to check 4.2.2.1 is pingable .We check that ip is pingable after the bridge is created .
You can change the pingable ip settings from configuration option from admin panel if 4.2.2.1 is not pingable and add any other ip which is pingable from your server .