With some Brother printers you can try this.
Access the internal maintenance mode by pressing the Menu/Set button, then press * 2 8 6 4 within 2 seconds. This should put you in the maintenance mode menu. Enter 80, and then scroll down with the arrow down (round) key. You'll find an entry listed as purge count. If number is over 6000, enter 2 7 8 3.
This will reset the purge count value. Then the printer will restart, hopefully without the annoying cannot clean message.
Some times this happens because of using cheap compatible ink cartridges if this is the case change the ink cartridges.
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All The Best: Pineworks