Question: The client cannot sign the eisgnature request (ie client is using a MAC and it restricts and treated as a virus)

Solution: 

Step 1: Ask a team mate to open the esignature link and share it.

Step 2: Please try a browser extension,  the incognito mode, in Google Chrome type CTRL + shift +N or even another browser.

Could you please confirm that this error occurs only for this specific document and other e-sign documents to sign work well for you?