Speedo isnt working

Ive fitted a new speedo cable and speedo drive, however the speedo isnt working.  The plug is in at the back of the clocks so im guessing the problem is at the gearbox end. I just pushed it in the hole and screwed up the closure plate. Is this right? 

did you make sure the drive end was firmly fixed to the cable?as i have seen loads of these fall of and end up in the gear box not attatched to new cable,worth a quick look,while you at it connect cable to small battery drill and spin it to double check speedo aint at fault?

I removed the drive end and checked that it was driving the speedo,  which it was.  I then put it back in and it worked.