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The news is unfortunately not very good: A 'print unable' or 'Unable to print' message on a Brother printer usually means a fatal error. To be frank, this sort of error often leads to a decision being needed, between having the printer repair-serviced, and replacing the printer.
First try opening the printer, and making sure that no loose parts, paper bits, paper sheets, debris, anything, is obstructing or obscuring the inner workings.
Second, while the printer is open, see if there is considerable (enough to notice) dust in the lower parts of the printer. If so, the 'encoder strip' might possibly be obscured by dirt and need cleaning... if this might be the case, let me know and I will instruct you further.
Third, was there a paper jam originally? if so, then if it was removed roughly, the machine may have been damaged, unfortunately.
And, wherever the jam occurred, and wherever paper was removed from the printer, would be the location that most needs a close inspection for anything wrong - broken parts, jammed paper presence sensor swiches, etc.
Lastly, leave the printer unplugged for overnight or longer. A 'rest reset' is about the last thing to try, before deciding between repairing and replacing a printer.