Double-check the IP address of the device you're forwarding to. Make sure it's static.
Ensure that the device is running the service you're trying to forward (e.g., a web server on port 80).
Verify that your ISP isn't blocking the port you're trying to forward. Some ISPs restrict certain ports for security reasons.
Check for any additional security or parental control settings on your router that might interfere with port forwarding.
If you've tried all of these steps and are still experiencing issues, you may want to contact your ISP's customer support or the router manufacturer for further assistance.