Hi there and welcome.
I’m not entirely sure how it works once, but in the Add Money event you read from a variable called Collected Cash and add it to the input parameter Total Cash, suggesting that the Collected Cash variable is the ‘running total’, but then it sets the result in Total Cash.
Your UI binding then seems to be pulling out a variable called Total Cash, so there is some confusion here, and you appear to have both Collected Cash and Total Cash variables on your character?
I would have thought the parameter name being the same as the variable Total Cash would shadow it and the set at the end would be effectively doing nothing (setting the parameter), but the behaviour you describe suggests it is setting the variable, so the problem is presumably the Collected Cash you are adding onto (always 0).
So, figure out what’s going with Collected Vs Total in your character, and choose a parameter name for Add Money that is not the same, even if you can (and make it work) it is just confusing matters.