Had the exact same problem with my new pump/filter combo. It would read 0 on low speed, and about 8 on high speed. The pool store, Rec Warehouse, assured me it was ok, but it didn't seem right. I read numerous posts here where pressure gauges frequently go bad, and in fact, it's not unusual for a new one to be bad right off the start. Anyway, I got a replacement from the local pool store about 2 blocks away for $10, and it now reads 4 psi on low, and about 12 psi on high, which seems about right. I will be taking the defective one back to Rec Warehouse and demand that they exhange it for a new one, which I will keep as extra one.
There are some recommendations here to replace every season with a new gauge.