Hi maggsie, I googled your issue and up came a bunch of things where numerous people were complaining about the very same thing.
You can find one example
here.Therefore it sounds like this might be some kind of glitch - have you tried looking through the Steam forum for the game, just in case someone else has posted ways to resolve the issue? I will take a look and see if I can find anything.
We can also move this thread over to Glitches if need be, as I am certainly not an expert on this topic.
Maybe someone else will be able to help, too.