Thanks for the quick reply Amber. I ended up resetting my DropBox password, and now everything is working as you explained. It was not a problem with the app.
In summary: If one has bought the $2.99 app, it contains all the DropBox capability already. It is not necessary to buy the $0.99 plug-in. You log in to DropBox with your email address and password used when you created the DropBox account.
In summary: If one has bought the $2.99 app, it contains all the DropBox capability already. It is not necessary to buy the $0.99 plug-in. You log in to DropBox with your email address and password used when you created the DropBox account.
App continues to work brilliantly. Thanks again.