Check the front sensors under the car, one on each side. If they are dislodged or damaged then the car won't go up, even if the pump is working. I wouldn't force the pump to start before checking this as it will wear out and you'd have to rebuild it.

By the way, are you getting a message on the dashboard?

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BMW X5 E53, 4.8iS - 2005
Professional Stereo/Nav with DSP (modified BM54 module) - Converted to Eonon GA5166X with Reverse cam
4-Corner Air Suspension - Converted to BC Coilovers