Have acquired a Protech Flux 5000 II analyser from a local MOT station, but I have a small! problem in that it completes the
10 minute warm up, leak test and zero calibration, then nothing, if I press the measure key it starts the process then immediately goes back to standby.
On start up the message "next calibration due in -680 days" pops up, so I am assuming that when the calibration expires the machine goes into sulk mode
Does anyone on here have any experience with this machine and able to give some advice?

There's one here for sale on t'Bay. See what he has to say about calibration. Perhaps he might be able to help you.

GAS ANALYSER Protech Flux 5000 II | eBay