There should be a check right at the city water connection. On mine, if I remove the filter screen it is visible, and I can actually push on it to release pressure if I want. Could be yours is stuck so pulling the screen and poking at it a bit with your finger might be helpful.
2020 Coachmen Mirada Select 37RB
2019 Ford Mustang
H&H Aluminum Car Hauler
Cricket RX5 Golf(?) cart