If you see residue on the liner anywhere, wipe with a little mild dish soap and water.
For a more thorough cleaning, submerge in diluted dish soap and water for 15 minutes to allow the soap to penetrate the seams. Allow 24 hrs to dry sufficiently.
Or, use an enzyme cleaner made for pets and follow the instructions on the bottle.
* Do NOT put the liner in dishwasher, dryer or washing machine.