Twitter and Facebook share sounds not working

iOS 9.2.1 and iPhone 6s Plus here.

My Twitter and Facebook share confirmation sounds aren't working.

Note that I'm not referring to the notification sound, but rather, the sound it's supposed to make after one shares something on Twitter or Facebook. For example, if I'm on Safari and I share a link to Twitter, the "Tweet" sound doesn't work. Same goes for Facebook. The "Swoosh" sound isn't working.

I've checked and double-checked my settings, and they are correct. Volume is up.

Any help would be appreciated.