Hey CBFlood-
Here is a screenshot of the setup that worked for me to call a variable from another function. The bottom section outlined in red is from the blueprint where the variable “CallFromElsewhere” exists. The top section is inside my character blueprint and uses a cast to the other blueprint to get access to the variable. As Arelius mentioned, the variable needs to be public in the function where it exists (the eye next to the name needs to be open). In my case “CallFromElsewhere” has a default value of 0 which shows when I press V. If I click the right mouse button and then press V again it shows the changed value of 9. You should be able to use a similar setup to control your GameOver variable.
Cheers