lol started using unity a couple of days ago and with the tutorials and everything it was all going merry and well. I followed the roll a ball tutorial word by word and letter by letter. the game worked perfectly, well....
at least in unity.
Thing is, I build the game and boom.
I have a working game with no collision detection(basically not working). didn't touch unity for 4 days now. Fuck I hate when this happens.

I actually had something fairly similar happen not too long ago. Finished a 2D brick breaker type game, runs smooth as butter in editor. Built it and suddenly the game thinks that the ball touching the paddle == ball touching the lose collider (which was outside of the camera view). Messed around with code trying to figure out what's wrong, suddenly touching the walls also trigger the game over-screen. Go back and forth, not getting anywhere. Finally end up rubberducking at my partner, make a build to prove my point and suddenly the game works. I have no clue what's up with that, but apparently it's a thing that Unity's physics engine can be a bit buggy?
I do wish you good luck though. :) Quadruple-check all tags and references and what-not, and look around if there any mentions of that specific bug and see if there are any workarounds to it. Hopefully you'll end up with less bald spots from all the hair-pulling than I.

They have been updating unity. The tutorials are all old.

Unity is absolutely great rant material.
Piece of shit.