Error : Unable to clean

Unable to clean means that the waste-ink "sponge" is full. If you've already checked for small paper part (which is very unlikely to cause this error message), the error is mechanical. Unfortunately, that's not something us users can change, but the machine would require to be sent to service. So if your machine is not within warranty, I'd doubt it'll be worth the service cost.

When trying to use your Brother machine you get the message "Unable to _____". The blank may be the word Change, Print, Scan or Clean and these words may vary from model to model.
This message is a general message and will appear for different reasons. It often indicates a paper jam or a mechanical issue. Complete the following to determine the possible issue.
Check for foreign objects, such as a clip or ripped paper, inside the machine.
Open the scanner cover by pulling up on the lower right corner of the cover. Look inside the machine and remove any foreign objects. If you see jammed paper or another item inside this area, gently pull it out and then close the scanner cover securely.
Then with the power on, pull the plug from the wall for several minutes. The plug it in and power the unit up.
hope this helps.. thank you have a nice day good luck