Hi, thanks for your reply.
I was going through all of the things that you'd asked me to do and nothing was working - including trying to run the AppleScript for the current track -, until I ran the activate Spotify code in AppleScript. It came up with an error but opened Spotify anyway. After that, everything's been working fine - all of the AppleScript works perfectly without error, and Spotifious works fine!
Thanks for your help!