You still don't say whether a server is running on the computer you have forwarded the port to, listening on that port. That is an essential part of the process when testing if the port is open on your IP address.
canyouseeme.org isn't listening on that port; it's testing whether your computer is.
Let's make an analogy. You forward telephone calls from one number to another. So when someone rings (let's call it 12345) that call is forwarded to 67890. Now you ask someone to test that by ringing 12345. The call is forwarded to 67890; but unless someone is listening to that phone, and answers the call, the tester will report that there is no answer. So you need the forwarding and the listening to the address forwarded to for the test to give the right result.