Gear and Wepon Editor not working

Hello,
I have just installed splathex and I have a problem with the options that interest me the most.
Indeed, when I want to use the Gear or the Weapon editor, I have an error message starting with this: "Error : System.TypeInitializationExeption"
And more there is an indication of error 404 Not found

Does anyone have a solution to make this work?

Thanks in advance!