If there is no vacuum to the controls, the air will only come out of the windscreen vents, and no others.
Check as above^^.
There is also a small, round, white, one way valve inline on the hose from the manifold.
That may be sicking and not allowing any vacuum to flow.
Put your ear right up to the selector dial while the engine is running and see if you can hear any air hissing.
This may confirm the vacuum "harness" on the back of the selector dial may be loose, or have come adrift.
Importantly, carefully check for splits, holes, cracks etc. in the hoses.
They do unfortunately, have a habit of splitting and cracking.