Something that is not apparent when you set up your account is the use of private posting keys. After trying to login to DTube repeatedly I set out to solve the problem. The FAQ was not very helpful and there is no available link to bring you to the following page, but this is where one needs to go.
You'll need to go to https://steemit.com/@YOURUSERNAME/permissions
You'll see public keys there, but if you click the little red "show private key" buttons you'll get your private keys which will allow you to log into Dtube.
Using these private keys will also keep your Steemit account more secure.