If the printing is not possible, check the following:

Is the compatible cable connected to the printer and the computer properly?
Disconnect the cable from the printer and the computer, and then reconnect it.
If the problem still occurs, replace the cable with a new one.

Are the compatible ribbon and media loaded properly?
Load the compatible ribbon and media in your printer. For details, see the FAQ: "How to load the Ribbon" or "How to load the Media".

Is the print density setting correct?
Check the printer’s printing density setting and adjust it properly.

You can check the settings in the BPM (Brother Printer Management Tool) as follows:

1. Connect your computer and the printer, and then make sure that the printer is turned on.
2. Start the BPM, and then click the Printer Configuration button.
3. Check the Density setting in the FBPL tab.

You can also check the settings in the LCD as follows:

1. In the LCD, select the Menu icon (  ).
2. In the Main menu, select Setting.
3. Press Command Set, and then select the programming language you want.
4. Select Density or Darkness.
5. Check the Density or Darkness setting.

Does the Print Head need cleaning?
Clean the Print Head. For details, see the FAQ: "How to clean the Print Head".

Is the Print Head's harness connector connected correctly with the Print Head?
Turn off the printer and plug the Print Head's harness connector to the Print Head again.

Does your custom program contain the necessary commands?
Make sure that your program contains the PRINT command at the end of the file and a CRLF at the end of each command line.