Having been unable to solve the http to https issue for too long, I removed GPUGrid from my list of projects, with the intention of immediately starting afresh. When I now try to add the project, I repeatedly get the message from BOINC, "Failed to add project". I do wish exception handling was a little more expansive, but wonder if anyone has any suggestions as to how to re-connect the project and avoid this message?

Update your BOINC manager to the latest version (it's 7.16.20 at the moment).
https://boinc.berkeley.edu/download.php

Thanks - that worked