Hello. My name is***** can help you with your question.
Please make sure the toner that you are using is a genuine brother brand toner and not a replacement or compatible toner. The brother cartridge has a fuse on it which triggers the printer to know that it's been replaced. Many third-party and remanufactured toners did not have this fuse in place. Otherwise, if it is a brother brand toner cartridge, then it's likely that it is defective and needs to be replaced. You should be able to get it replaced at the reseller from whom you purchased it. If you have any questions or if you need additional help, please let me know.