Empty browser page when signing

A customer of ours recently purchased an Adobe Acrobat Sign Enterprise license. In the signature route there are some seven signers, all are able to sign except for one when he clicks on the "Review and Sign" button in the email invite, a blank web browser opens up, no agreement content, nor the signature field are visible. 

The customer tried the same on both Chrome and Edge and had the same effect as shown above.

As I mentioned all other signers within the same organization and the same network had no issues.

I asked him to try another machine/device and am still awaiting his feedback.