Invalid Parameter @ btnLogin Issue

Sorry for asking what might be a common problem but iv’e installed PMU on two separate computers. the 1st seems to have installed correctly but the other is having an error with an “Invalid parameter @ btnLogin”.
I have tried my login and my friends on both but theirs is having the problem, also tried hitting “sign in” while leaving the inputs empty and getting the same results.
i have also tried following this guide with no luck on fixing.
https://forum.pmuniverse.net/t/resolving-the-btnlogin-errors/38073