a) You could be using the wrong Buffer account
If this is the case, and you can log into the Buffer account that you don't want to use, you can disconnect it from Quuu by going to ‘My Account’, then ‘Apps & Extras’. Click ‘Revoke’ next to the Quuu logo. You should then sign into the correct Buffer account and then you’ll be able to return to Quuu and connect the correct Buffer account. See here for more info on how to do this
B) You might be signing into the wrong Quuu app
Quuu is comprised of two principle apps: Quuu and Quuu Promote, it’s easy to get them muddled up, so just double check that you’re on the right app. Quuu is for content suggestions and Quuu Promote is for promoting content that you’ve created.