Yes, true - it's seeing the battery voltage so that indicates it's all fine there.The Vic is or has been connected to the battery fine for weeks and showing Volts/state just no PV . There is a fuse which is fine . I think this all stems back to when I first fitted the Vic and mixed up the cables between PV and Batt so the PV had Batt connected , that gave issues with the 30A fuse blowing until I realised my dumbassery .
It's possible when you connected the battery to the PV input that it did fry it, they have reverse polarity protection but I'm not sure about incorrect PV and batt connections.
The 75/15 has a max short circuit amp of 15a. Your battery would have been trying to put way in excess of 30a to the MPPT when it was connected (hence blowing the 30a fuse) and Victron do say that connecting a panel with above 15a short circuit amperage may damage the controller, which is essentially what you did when you connected the battery.