That’s the only error I saw in the screenshot you shared. Then I reread and realised, so I apologise for that. Also for some reason I didn’t see the code, just the screenshots. Just FYI, that GPU error is going to be an issue if you are seeing it on the basic level.
Now, the issue you are seeing about messages.
Have you deleted the binaries and intermediate folders at all?
This is the only thing that jumps out at me to start with.
Other things to try. A packaged build may demonstrate if the issue is with the code or something else. A glance over your code seems to indicate it is fine.
Next, you need to compare against the end of lecture code. This may point to an issue with your code over the lecture.
There are some UE5.3 specific issues as well. You need to exit steam when trying to test and also have noticed that sometimes the behaviour is incorrect in the editor so you have to use command line to run the game which is covered in a lecture.
Give these a try one at a time and let me know how you get on.
Edit: ChatGPT is actually wrong. The hasAuthority should return true on a server instance and false on the others.