Kitchen aid k45ss classic unscrewed black plastic screws and springs on housing and replaced and now it won't run

Hi, JDMCIN. I hate it when that happens. It seems that power is not getting to the armature from the brushes so I would suspect that one or both of the brushes is (are) not seated properly. I'd suggest removing them again and making sure the contacts are facing in the right direction to contact the armature’s commutator. The concave contact face should be resting completely on the commutator. If you've turned it 90 degrees too much, it won’t' seat properly and the motor doesn’t get any juice.
Good luck, I hope this helps. Howard, Burke, VA\
If this solution has been helpful, please rate it, thanks! - hslincoln