Are your city water attachment and your fresh water tank fill separate, or do they use the same connection?
If they use the same connection, there will be a valve nearby to select city water or tank water.
Even if they are separate but next to one another, there may still be a selector valve.
If they are on opposite sides of the coach, then you probably have a pump issue.
Checking the filter that is just upstream of the pump FIRST is a good idea.
Do you have a valve or drain that you can open just
downstream of the pump? If not, can you get the pipe off the downstream side of the pump?
Either way, open the drain or remove the pipe and run the pump briefly; if water comes out under pressure, the pump is ok. If no water or little water (and the filter is clean) you will probably need to rebuild or replace the pump.
If its original equipment, there are better and higher gpm models out there to replace it with. Like this one
. An easy DIY.