Updating this post.
After spending nearly 2 hours on Simlink “cannot connect” issue, I now realize you need to be in the cockpit in MSFS 2024 for simlink to work. It does not connect when your character is walking around the plane. Ughhh! I wish I knew that before trying every single troubleshooting step listed above!!!
I now consider this issue “resolved”, but I’ll leave my post up so others can see how frustrating this is. This is because I always make sure everything is working before starting my flight, and when I checked the moving maps on Charts and it was not working, I started practically started banging my head against the wall trying to find a solution when there was no underlying problem.
Overall, if you want people to stop asking about this, somehow inform them that they need to be in the cockpit for Simlink to work, or change something so Simlink works while the character is walking around the airplane - not that the latter is necessary, but it would help others avoid going through all of the troubleshooting steps that I did which were unnecessary.