This is actually a solution, not a problem, since I was finally able to figure it out....
I was receiving a 'bad checksum' error when I tried to deploy my first application to shinyapps. I had tried removing and reinstalling rsconnect, as had been suggested elsewhere, to no avail. But checking my packages, I found I can 2 versions of curl installed, one of which appeared to be quite old. I removed both of those, as well as rsconnect, reinstalled both the curl and the rsconnect libraries and everything worked!
This should help those who find no solution listed on topics: 27021 and 21740.