tbh Mike, with you vendor i think it time to treat as a waste of time, so cut your losses (in a time sense) and look for another one.
annoying to be let down i know, but 5's in various conditions are turning up all the time on Ebay etc. so being pragmatic and adding a bit of patience, will serve you well imo.
given the laxity in responding ,this machine might well have been a 'pig in a poke'.
regs
Alan