The E4 error on Brother embroidery machines typically indicates that there is a problem with the hoop or the hoop sensor. The hoop sensor is a small switch located on the embroidery machine that detects the presence of the embroidery hoop. If the machine cannot detect the hoop or if there is a problem with the hoop itself, the E4 error will be displayed.

To troubleshoot the E4 error, you can try the following steps:

1. Check the embroidery hoop to make sure it is securely attached to the machine. If the hoop is not attached properly, the machine may not be able to detect it.
2. Clean the hoop sensor with a soft, dry cloth to remove any dirt or debris that may be interfering with the sensor’s operation.
3. Try using a different embroidery hoop to see if the problem is with the hoop itself. If a different hoop works without issue, then the original hoop may be damaged or defective.
4. Check the machine’s manual or online documentation to see if there are any firmware updates available. Installing updates may resolve the E4 error.
5. If none of the above steps work, it may be necessary to have the machine serviced by a qualified technician. They will be able to diagnose and repair any underlying issues that are causing the E4 error.