Hi. We are renting a condo, on the 3rd (top) floor of a building. We have 2 bathrooms. The sinks in both rooms are fine, however, the tub/showers have an issue. The smaller bathroom only gets hot water to the tub, while the master bath only gets cold water. We have no access panels at all to check. The condo maintenance man tells us it's not his issue, he knows nothing about it. We had a plumber come out, and he was also unable to sort this out. There is an access panel to the attic space in the common area outside our front door. Could it be that someone has somehow gone up there, and shut off one valve to each room? It makes no sense really, but it's the only thing I can think of at this point.

Anything is possible. You did have the plumber check into the attic plumbing? Did he also take both valves apart to test incoming water? Do the valves have integral stops? When there are no access panels, eventually they will be needed if all other checking proves to be null.

If they are pressure balancing valves, the spool is stuck to one side in both of them.

If the balancing valves are stuck you need to remove them from the valve body and soak them in vinegar for at least 4 hours. Then wash them with clean water and also before you re-install them I would have someone go out and turn on the water while you and another person holds a towel over the opening. Have them turn the water on and immediately turn it off. Check the towels for debris. good luck...