I suggest you use 127.0.0.1 instead of localhost as it's being deprecated (maybe it has something to do)
I changed the default port to 8001 too because 8000 seemed to be used by some games or programs I use.
Also, try using the "Copy Request" button inside the states (it was added after that post you followed) just in case there's some kind of typo.
I hope all this helped 😅