Cannot delete silence between clips

Don’t know why because it has been working properly all morning. Now I cannot delete the empty parts between clips and have no clue why. I had been selecting audio or silence and hitting the back space. What could the problem be now?

I solved this by going to Preferences - Track Behavior and checking Editing a clip can move other clips. Now it’s working properly. Thanx!

Yes. In older versions of Audacity that was the default, but the new development team decided to change it.