After upgrading to firmware 1.4.2.20, you can only manage the RV320 from VLAN 1. We have always had VLAN 1 excluded from all ports and had Device Management enabled for VLAN 101.
After the upgrade logging onto the RV320 Web GUI it returned a white page stating you don't have permissions.
Our workaround was to TAG VLAN 1 on Port LAN 1.