I agree with @WhatKindOfKylie? that it was too soon for that kind of track as only the 2nd single, coming off a mega #1. It would have been like Rick putting out...um, It Would Take A Strong Man as the follow-up to Never Gonna Give You Up or something.Can't forget you flopped as it was a 'fanbase' track. You'll never stop had huge broad appeal but the goodwill for that wasn't there for the follow up. It was bought by Sonia 'fans' only.
Exactly, as much as I love Can't Forget You, Listen To Your Heart would have made more sense as single #2. I know it only just made it to the top 10, but it did have a pretty decent chart run overall, 8 weeks in the top 40 over late 1989/early 1990. Wonder sometimes if it could have been bigger if released earlier. We'll never know of course!