A shotgun approach to solving this problem:
If you are plugged into shore power, even a bad battery should typically facilitate 12 volt current flow via the converter. Exceptions might be if the battery is totally wasted with blown cells and such, but even then, when connected to the "charger", the charger should supply 12 volt power "around" the battery....straight to the coach.
Assuming the pump is truly OK:
Verify that the converter and shore power are working by plugging in a 120 volt load to one of your outlets. (be sure the GFCI is not tripped before you assume anything) If shore power failed somewhere along the way, not only will your 120 volt loads not work, but the battery will rather quickly lose its charge due to parasitic loads such as the CO/Propane detector. Your battery could be deader than dead.
If shore power seems to have failed:
Look on the RV end of the shore power cord to see if the tell-tale (usually blue) LED light is on. (typical installation in Forest River products.) If no, check your house outlet and any extension cord with a light or power tool. Did you trip a ground fault on your outside circuit? Again, no power to the coach will quickly kill the battery unless it's disconnected from the parasitic loads.
If the tell-tale LED is lit, cycle (turn fully off then on again) every breaker in the panel. But it's important to know that there are typically fuses/breakers on the input side of the converter...protecting from bad shore power. You may need to pull the panel to be check the input fuses/breakers. Save this for later, because it's a bit of work and not likely to be the issue. Remember to cycle any breaker, because it's often hard to tell if a breaker is tripped.
I presume this is not the problem, but it's good to start at the beginning.
All of the above will take only a few seconds if things are working. If things are not working, obviously those problems need to be solved...first, most obvious culprit, the GFCI feeding the home's (or storage facility's) outdoor circuit.
As others suggested, verify that other 12 volt loads are working properly. Do you have lights? Will the furnace run? If so, skip to the last three paragraphs about the pump. If you don't have 12 volts anywhere, continue here.
Check and clean the battery terminals...always a good maintenance practice, so not a waste of time. Crudded up terminals can block charger current from making it past the battery connections and into the coach. The same can happen if one tries to jump start a car with crudded up battery terminals...the power from the other car doesn't make it past the corrosion. Also bear in mind that where crimp connectors are applied to the end of a wire, there may be heavy corrosion between the wire and the crimp connector, so soak the terminals in a baking soda solution for a while. If you can't get them clean enough to not bubble, you might need to cut the wire back and apply new terminals...available at the hardware store.
While you're at it check the electrolyte level in the battery. If it "ran dry"...plates exposed...it could be fried so badly that it behaves like a black hole when charging power is applied. A water pump needs 7 amps or more to run.
Verify that the main fuse/breaker near the battery box on the tongue is not blown/tripped. This would prevent current from going to the coach. Similarly, if you have a battery disconnect switch, did you turn it off and forget to turn it on?
Check all your fuses. 12 volt spade fuses are difficult to check, so pull each one and shine a flashlight through it from behind to get a really clear view of the fusible section in the plastic case.
If all of this fails, perhaps your pump died or there is a problem with its 12 volt connection. Find the pump. It will likely be on the floor, and you'll know the location easiest by looking under the rig to see where the line from the fresh water tank enters the coach. The pump will be there - perhaps under the "floor" of a cabinet. And silly as it seems, it may be right behind the breaker panel. If you know where your water filter is, it will likely be below the filter.
Wherever it is, open up the cabinetry so you can hear it. Turn on the pump. Do you hear it trying to run (a hum of a stalled motor)? If so, minerals in the water may have seized up the impeller or caused some other problem. If you are trying to draw water/antifreeze thru the pump, perhaps the input screen is clogged? (Info on this is easy to find in the forum and elsewhere on line.) Most pump failures are gradual, but nothing says the pump won't just quit...especially if it seized up and power was applied for very long...it would suffer a meltdown in the motor. Cleaning a clogged input screen, however, may solve the problem. These pumps can "run dry" for a while without suffering too much damage...they are not built to precision tolerances like a well pump.
If you don't like the condition of your pump, new pumps are available on Amazon for $70 to $125. I replaced mine with precisely the same SurFlo pump for $70. Be careful what you choose, because Amazon has 120 volt pumps sprinkled in with 12 volt pumps. It's best to look at your pump first and then order an exact replacement. There is a "data panel" on most pumps giving the brand, model, and specs (e.g. gallons per minute, amps, etc.) While you might upgrade, remember that "more power" takes more power (amps) and burns thru water more quickly. If you have a big 5th wheel, you'll have the fresh tank and battery bank to warrant a big pump, but if you have a small rig, your small fresh tank and single 12 volt battery will appreciate a factory spec pump.
Have and know how to use a decent multimeter (all of $15 or $20 for a really good one). There are numerous YouTube videos on the subject. Rather than choose one, hear's the search: https://www.google.com/search?q=vide...hrome&ie=UTF-8
It took a little while to write this, so perhaps you have already solved the problem, but if not, I hope one of these ideas is helpful.