Peugeot escapade combi?

My diesel car Peugeot escapade combi 2003. has been off road for last 3yrs Just taken to M.O.T. garage a round trip max 3 miles. Why would in a year from Feb 2022 M.O.T emission rise to failure in that period when its mileage was 3miles to and from M.O.T. It was started and Ticked over 5 mins each month or two since Feb 2022 M.O.T with a pass for 2022yr.
What can I do to drop emission. Would this have any benefit- -----changing air filter/s. ?
Odometer shows 79,000, considerably low compared to others of that year going in to 100k +
Thanks in advance.