Hiya,

Mounting has no effect.. ive had them in alsorts of positions.
Check the rating on the actual valve.. 24v and 50bar.
Next id put 24v from a good battery driect to the connectors.. pos and neg, not the 3rd earth if it has one and there will be a large click, and you feel the coil activate.

If it clicks, come back, if not, send it back as faulty.