OK well your halfway thru my standard list
Make sure that;
The engine is running.
The handbrake is on and the brake light on the dash is lit ??
If the brake light isn't coming on, then check the little switch at the back of the handbrake (remove console) on passenger side they get dusty and dirty.
Now press Up the bleeping should start ??
If not then check the fuses (not likely but easy to do)
http://www.g8dhe.net/bwm/ .
Else if not clean the switch
https://www.youtube.com/watch?v=tX1SB0xoJOU
If they are OK and its bleeping, then check the rubber seal isn't stuck to the roof with age, run a card around to release it.
If that is OK then operate the Up then Down switch LOTS of times, it might be a dirty switch contacts or it could be corroded motors, by turning the motors even a little bit it might free up the corrosion and let you get the roof up. If so then drop out the motors at the rear and check for corrosion, there is a good Fact sheet if your a member of BongoFury on the process. Otherwise if the roof won't go up still then the is a method of lifting it but its not easy!
What ever you do please don't push on the roof itself, until the sliders are out of the locking shrouds, otherwise you stand a good chance of damaging the seal around the skylight, if the gas struts are tired and need replacing then a little assistance for the last few inches is acceptable.
Finally mechanical things NEED to be used, it causes the oil grease to spread out rather than pool and helps to reduce corrosion. Don't leave things unused for months on end....
Finally if nothing works then
https://www.youtube.com/watch?v=PaSzghJ2tE0