New iMac, getting error message saying to give Sophos full access in preferences. Does not resolve issue.

 I got a new iMac (MacOS Mojave 10.14.4) and ported everything over using Apples migration tool.  

All is well except Sophos Anti-Virus Home Edition 9.7.7 gives me an error message asking me to open the Mac's security preferences and give Sophos full access so that it can scan.  Clicking the link in the dialog box opens preferences and I have given Sophos full disc access.   It has not resolved the issue and the dialog box reappears approx every 15 minutes or so.