The customer has an F5 load balancer and a virtual webapp that only fails when users come from the outside. The virtual application works fine from the inside of the network.
There are internal errors when it does not work that show the error : Disallowed Key Characters
This means that the application ( AlgebraNation ) is rejecting the requests because there is a cookie with a ~ and $ in the cookie name.
Once the customer fixed the F5 to not use ~ and $ the application starts working again.