Try posting photos of the actual internal wiring of the device so we can see the colors and which wires go where. I can take mine apart and look at it but it is raining and we are hooked up. I need to see which terminals go where. Mine may be different than yours as it is quite a few years old. I do not know what they are doing these days and I can't remember how I wired mine.
To get from the 30amp to make it work to your 50amp it has to be wired the same way a dog bone is wired internally. I know how but I am at a loss for being able to put it into words. Basically you just take one incoming wire and then splice it where it goes out to split it into two wires. I did this in the box I think but I forget how I physically did it at this point. I have to tear into it to remember.
You do not split neutral or common - you only split hot - but you DO NOT DO IT if you do not know exactly what you are doing. Don't play around guessing with electricity. How many people are killed every year messing with this stuff? You need a fully qualified US or Canadian electrician to do this if you are not 100% sure you know exactly how this is done.