you’re correct in that the [SetInputModeGameAndUI] node has been deprecated but the one you are using is the correct one or updated version.
(the old one would have a yellow warning on it about it’s deprecation & would show in red as well)
but that node is for setting focus for the mouse so you can use it a specific way, it shouldn’t have any relevance whether your menu shows or not. you have done that with the [AddToViewport] node already.
but that tutorial is old & hasn’t been update or fixed. I’ve watched that video series before & it’s a long and detailed tutorial which requires a ‘specific’ setup so if anything is not hooked up right or not set right then there would be problems.
I did notice in the comments for that specific one (15) someone mentioned something about the game mode - if you created a new game mode then make sure you have it set in your world settings (settings can be found in edit tab at top or top of viewport).
but that’s just one of the things you can check. after watching a bit of this series there’s a lot that can go wrong & if it’s not something simple that you can do like with checking the game mode I mentioned then you would have to do like Jamendxman3 said above & trace and/or debug till you found what the issue is.
best thing I can do for ya other than the advice above is to wish ya luck 