You might have something here, I'm testing if my characters are within 5 feet by finding where I have (enemy is too close) with ranged attacks. I'm seeing the same problem where I'm denied sneak attack.
Edit:
From what I'm seeing, the enemy needs "threatened" status or you need to have advantage to get Sneak Attack. "Threatened" doesn't provide it all the times that it should.
So it's basically bugged? I took a screenshot and it has the threatened status. I was also using melee sneak attack as that's the type of rogue I'm playing.
