It sounds like the run capacitor for your A/C fan has failed. That's typical when the motor hums but won't start.
You need to make sure the the fan motor run capacitor is a 20 + 10 MFD 370v - that's the size the manual says it is but
I would verify anyway. It is located next to the control board - remove the top cover and it should be on the side of the enclosure.
Dometic sells the capacitor for about $60
but the same capacitor is available from Amazon, etc. for about $14.