Problem accessing a web site using TMG

[Disease]

Pupils at our school are trying to access https://wex.s-cool.co.uk/learner for work experience the trouble is TMG for some reason blocks it. IT works fine on teachers machines who do not go through the TMG, they use the LEA proxy.

 

I tried turning off the category blocking rules, nothing.

 

I added a new rule explicitly allowing the website, nothing, if I run the troubleshooter using a pupil account and it says it's allowed.

 

When you go to the site it loads but loads blank as if it is stripping out all the code on the page.

 

Any ideas?