There may be many reasons why a computer pattern machine cannot thread the bottom thread when starting a needle. The following are some possible problems and solutions:
1. Thread and wheel detachment: Check if there are any small components detached from the sewing machine wheels and reinstall them; At the same time, confirm whether the stitching in each lead port is correctly routed and fixed.
2. Line connection error: Check if the electrical circuit connections of each part are good.
3. Loose tension on the top line: Increase the tightness of the top line appropriately to generate sufficient tension.
4. Dust or shredded cloth blocking the holes of the sliding plate: Clean up any residues such as dirt, cutting lines, etc. in the sliding plate pipeline and hook area.
5. Damaged fork teeth or wiring board: Check and replace any damaged components.
If the above methods are ineffective, it is recommended to hire professional technicians for maintenance and repair. Meanwhile, please note to turn off the power and unplug the power plug before making any adjustments or modifications to the machine to ensure safe operation.