Hi Topper80,
It's very unusual for two systems to fail - both normal gear lowering and the standby system.
Something vaguely similar happened to a 757 many years ago at LHR. The gear wouldn't come down normally, but the back up free fall system worked OK initially. During the approach the gear retracted so the crew went around and into the hold.
A conversation with Boeing in Seattle requested the total depressurisation of the hydraulic system which the gear was on. The free fall gear system worked and the gear remained down and locked for a successful landing.
There was a fault on the selector valve which caused the hydraulics to raise the gear even when selected down.