Excel - Unable to access Office Add-ins

Morning all,

I'm having an issue for months regarding accessing Office Add-in portal within excel as I'm getting "Cannot connect to the catalog" error. I've done all of the test that I can think of including testing on a separate PC. Logging with my domain account, I can access and install an Add-ins within excel but when the user is trying the same on the exact same PC (using her Domain account, of course), we're getting the same error.

No problems with the network, Office has already re-install on her laptop and for the laptop that we use as a test, it is a newly build machine.

Thanks and regards,

Mark