Delete key won't remove space inbetween clips/media

Normally you can click the space between media in the timeline and the Delete key will quickly remove that space and snap the clips together. Unfortunately sometimes the Delete key no longer works in this way, no matter what I try. Any idea what I'm missing? (Example added below)

I can't found the solution anywhere but I may not be properly explaining or using the right phrasing for the tool, so my apologies in advance.

Thanks for you help!