I'm vaguely recalling that this means that your ISP is censoring ports.
Maybe the port is closed, and it's a new policy to reduce port-scanning? If so it is one that makes it hard to detect that a port is closed.
Undiscussed Horrific Abuse, One Victim of Many Fri, 29 Apr 2022 03:11:49 -0700
I'm vaguely recalling that this means that your ISP is censoring ports.
Maybe the port is closed, and it's a new policy to reduce port-scanning? If so it is one that makes it hard to detect that a port is closed.