I got a bit confused when updating my plugin, so I’m making a note of it.
Code plugins written in C++ will likely undergo several version updates, and here’s a point to note during that process.
When updating content for an already listed Engine version, the Project File Link on the screen below needs to be a different link URL than the previous one.

It seems that if this URL is the same as the previous one, notification that the content has changed will not be sent.
I use Microsoft OneDrive, and overwriting a cloud file results in the same shared link URL as before. Therefore, I issued a different URL by first unsharing the file and then sharing it again.