My Retry Button/Trigger won't disable

You forgot to set the default value of Attempts to 1 (as Nedim instructed). 

When the default = 0, that gives the user 3 clicks of the Retry button before the Attempts variable = 3. That's 4 attempts of the test. 

If you reset the default to 1, the variable will reach 3 after the user clicks the Retry button twice.

You can see this in the attached version. I switched the default value to 1. I also added a temporary text box to the Failure layer that shows the value of the Attempts variable. That's a helpful way to troubleshoot when you're working with variables. 

One more thing I did: I edited the Disabled state of the Retry button so it looks different when it is disabled. 

I suggest you also add triggers so the "Please try again" audio doesn't play when the Retry button is disabled. Instead, show a message that explains what the user should do after failing 3 attempts.