I guess the Character is not a MainCharacter. Cast Fails. Ref gets never assigned. Text will never display. Make sure your GameMode spawns a MainCharacter and not something different.
How did you check that your Cast was Successful? Access None simply means the thing you try to read from does not exist → Ref is Empty/NotAssigned/Nada/Null/None 
Can you show me the error you getting (the Log). Something fishy on your side. What you got should work 100% (at least the part you showing here)
I mean the Error you get after Quiting the Game.
Thats very odd. Are you sure you dont switch Characters or doing something else odd? Is Multiplayer and Replication a thing in your Project? Are you destroying your Character at any Point but still displaying the Hud (if you Destroy Character ref gets invalid)?
Hmm there got to be more to it and its hard to debug your case remotly now. I verified on my end it works correctly without issues. On your end you have to figure out at what Point your ref gets invalid and what caused it. You can use a isValid node before you read from your ref and return a different text that says Char Ref is gone or similar.
hello i’ve completed a simple tutorial that display HP as text number, it was really simple but it appears that there is an error through the blueprint. I was quite surprised since it is so simple so here it is.
Anyone sees what is wrong with it?
the game mode spawns a Main character, the text though is displayed, the cast doesn’t fails but when i quit the game the the accessed none error pops
did a print screen on cast success and cast failed but the print always shows the success message
well i did a test package and no errors were shown.
Nope i dont destroy character at anytime and i started to build the project as offline
Is your CurrentHP maybe on private by any chance?