1999 Plymouth Voyager EVP wont set

I purchased this vehicle from a private party and have spent some money and time to clean it and make small repairs.
Now I have registered it and am trying to get it inspected.
A local small garage scaned it for emissions codes and there are none however they tell me that one of the OBDII system parameters wasn't set and that I needed to drive the vehicle to make it set.
I have been driving it now for 2 days and over 200 miles and the EVP won't set.
The tech keeps telling me the only thing that will correct it is to drive it until it goes through it's set up.
There must be something else wrong to keep the system from performing the set up properly.
Any advise?
Kevin