User getting error in Chrome - auth.services.adobe.com refused to connect

The web application has integration with AdobeSign API.

Flow of operation is-

1. User logs into AdobeSign and gets an Access token.
2. Then selects a document to upload to AdobeSign- which succeeds.
3. After this the signing url should open in an iframe where the user can add signers etc.
4. But this is where one user is running into error that says- auth.services.adobe.com refused to connect.
5. This error happens only for this user and only in Chrome. Seems to work in IE.

Any pointers would be appreciated.

Thank you in advance!