Is the light "CLEAN Filter" or "EMPTY"?
These may help:
http://www.ukwhitegoods.co.uk/forumsphpbb3/viewtopic.php?f=34&t=7134
https://www.how-to-repair.com/help/condenser-tumble-dryer-how-to-replace-the-pump-unit/
https://www.justanswer.com/uk-appliance/5oe2s-condenser-dryer-empty-water-light-staying.html
You can get more results by doing a Google search for - say - " Candy condenser dryer" Empty filter light on all the time" - but you obviously did that bepore posting here and expecting other people to do it for you :-)
You could also tailor the search by adding the model number and EXACTLY what the light is supposed to be
acp, August 2017