Another Proxy Message that won't go away

Corporate network, 100+ users working happily.

One user of Acrobat Pro, signs in via help/sign in and is immediately prompted for proxy creds.

I had it once before and I'm sure i deleted a file or folder maybe under common files - but can't remember and can't find it now.

Why is it so hard?

Don't respond with "whitelist these url's.................." the rest are working fine, it's another Creative Cloud opportunity !

Because we love spending time on this sh*t.