Sometimes vending machines refuse bills or coins, or the bill acceptor gets jammed, stopping transactions. These problems usually happen because of dirty or worn sensors, damaged bills, misaligned components, or issues with the coin mechanism. Following a few simple steps can often fix the problem quickly.

1. Check Bills and Coins
   Ensure bills are flat, clean, and undamaged. Check coins for correct size and condition. Proper currency reduces jams or payment refusals.

2. Clean the Bill Acceptor
   Turn off the machine first. Use a soft cloth, cotton swab, or cleaning card to gently wipe the bill path and sensors. Remove dust and paper fragments.

3. Inspect and Reinstall Components
   Make sure the bill acceptor is correctly installed and aligned. Check coin and bill paths for obstructions. Misaligned or loose parts can cause jams or refusals.

4. Test Payment Transactions
   Test the machine with different bills and coins to confirm they are accepted. Check both cash and cashless payments to ensure smooth operation.

5. Schedule Regular Maintenance
   Regularly clean and inspect the bill acceptor, coin mechanism, and sensors. Replace worn parts as needed to prevent future jams or payment issues.
   
   
6. Contact a Professional Technician if Problems Persist
   If issues continue after cleaning and testing, contact a certified vending machine technician instead of attempting internal repairs yourself.