OK - exact steps I've followed on Firefox and Orion side-by-side.
Firefox is fine, Orion gives the above error.
- Visit https://all.accor.com/a/en.html
- Deny/ reject cookies on the pop-up
- Click sign in/ sign up (at the top right)
- Pick sign in
- a) On Firefox, goes to login screen
- b) On Orion, goes to the above message
I wonder if they are doing something funny with the referrer? Looking at dev tools, I don't see the referer all.accor.com coming through on login.accor.com.
Visiting login.accor.com directly on Firefox also gives the above error - I think that the issue could be that imperva (their site guard thing) is checking referer or another parameter that is not being passed along by Orion, but is by Firefox.
(I tested this in compatibility mode on Orion btw)