It should not matter if you have the solar inverter charger disconnect. IF the unit was being stored someone might have removed the cables to prevent the batteries from overcharging, if they can not be checked and the solar panel was charging you could damage the battery over time.
You should have AC power as soon as you plug the cord in, just like when you start the generator. IF you do not have to plug a cord into ann outlet near the generator to allow AC power into the RV then you have an ATS ( Automatic Transfer Switch). The ATS detects the incoming AC power source and will switch between shore and generator AC power. Sometimes the relay can fail and you will get NO ac power on one source. To check you would need to locate the ATS and see if you have AC voltage in and out of the switch, if you have incoming AC power and nothing coming out it has failed. Location will vary on the ATS sometimes it is near the shore cord outside and other times it can be inside the RV behind the breaker panel, under the bed etc. The shore and generator cord will go right to it so try and follow the cables the best you can.
IF you do not have an ATS then you are looking at an issue with the cord or a loose connection at the breaker panel where the cord is coming inside. I might also get a polarity checker, it will plug into the outlets and tell you if there is a wiring issue, most Home Improvement stores have the checkers, if it picks up an issue and everyhting is working fine on generator then I would be looking at the shore cord.
IF you are using any adapters or extension cords on the main cord then I would get rid of them and plug in direct and see what happens.
Since everything works on generator the disconnected controller or solar charge wires should have nothing to do with this. I would thing someone disconnected them to prevent the battery from charging while in storage....
Hope this gives you some direction IF you have more questions or concerns please feel free to contact me, I am around daily and respond when I can. IF you are satisfied with my efforts please feel free to select a rating, it isthe only way I get credit for helping.... Robert