copy paste doesn't work SO FRUSTRATING

@dizoe I have a follow up question that I cannot reply to at this time so I included the image below. I didn't do any of the tests yet but I imagine it is the same issue because the keyboard short cuts appear to be working as when I hit command c to copy the edit dropdown at the top of screen highlights indicating it is copying. If I were to remove login items--well, I just don't think this is an option--my only login item is Dropbox where ALL my files are stored. Does this mean Dropbox is the reason I can't copy and paste? I'm preparing for a job interview presentation and still have to shower then drive 4 hours prior to a LONG day of interviews so I'll likely give up on copy/paste for today and just type all of this out. I love having a $4500 Macbook for less than a year with countless issues--insert sarcasm here.