I am having the same problem with local server connection failed and have narrowed it down to one of the node packages.
So getting this message:
Then get this message:
If you hit move to bin you can forget about getting it work at all - spent 2 hours trying to fiogure out why it was not working.
If you hit Cancel, then it works BUT the next time you close Wappler and start again and start the local server it comes up with the same message.
Using a mac up to date OS.
You can replicate it by just switching the server off and on it comes up with the warning and if you “Cancel” it works.