The E41 error on a Brother embroidery machine indicates that the upper thread is broken or has run out. Here are some possible causes and solutions:

• The upper thread may have broken or run out. Check the thread and replace it if necessary.
• The upper thread may be tangled. Remove any tangles or snags and re-thread the machine.
• The upper thread tension may be too tight. Adjust the tension as needed.
• The upper thread path may be blocked or obstructed. Check the thread path and remove any obstructions.

Once you have addressed the issue, clear the error message by turning off the machine and then turning it back on again. If the error persists, consult the machine’s manual or contact a qualified technician for assistance.