First do what I would do. See if you can contact the maker and do what they say.
If that doesn't work, put the accordion on top of the fridge for 2-3 days. You live where a major river meets the sea in a notoriously wet climate. It may be that the parts have absorbed too much humidity and are swollen. The top of the fridge is likely to be the warmest, driest part of your house. See if it doesn't dry out some and start working again.
Forget that if you have been running central heat and your dwelling is dry. If you touch a doorknob and get a shock, you'll know it's dry.