How to remedy gloopy nail polish?

I have purple Barry M nail polish which I absolutely love, but I can't really use it anymore as it's become quite gloopy, and not liquid-y anymore. I've had it for a few months, but I've other nail varnish for much longer which is still perfectly fine? Oh, and I already tried putting the nail polish in the fridge for a bit but it didn't help. Any ideas how I could fix this?