Footrest not rising on Sherborne rise/ recliner?

Hi. The footrest no longer rises on my Mum's Sherborne Keswick dual motor riser/ recliner.
The back still goes down and up, the chair rises to full eject position. Hand set still functions, though if rise is selected it will no longer returns to base position until chair has reached maximum rise position.
Please can you help?
Thanks
jane c, July 2022