There are over 2000 tracks in my liked songs, but they are all grey. I want to delete them all, but nothing works. They are not local files, and also not songs that are not available on Spotify, but it does say so.
Hey, I'm really sorry to hear that. We have encountered several complaints regarding the same issue. This problem might either be because your Spotify is not updated or it's a bug which Spotify is working on fixing and will fix sooner or later. Spotify is continuously working on updating its applications and provide bug-fixes to all updates on all platforms across the globe. But there are a couple of things you could try out.
1. Make sure you have atleast more than 250 MB of space remaining on your device.
2. If you have Spotify installed on your phone, try re-installing the application.
3. Make sure both your PC and Phone are connected to the same WI-FI network, try playing songs over different devices.
4. Make sure you've de-selected 'Offline Mode' as well as 'Show local files' options on your devices.
5. Try deleting all the cache memory.
6. Lastly, try changing your offline storage settings. You could change the storage location.
I'm attaching some images below for better understanding.
If the problem still persists, please visit the hyperlinks mentioned below. I'm sure they could be of some help. If it still doesn't work out, then it's surely a bug which will definitely be fixed in the future updates.