I'm running Mac OS X 10.12.6 now (Sierra) and installed Symantec Encryption Desktop 10.4.1 MP2 HF2 [Build 824] because the tech support people at Symantec said it would be OK to move from Mac OS X 10.10 to 10.12.x and use their product so that's what I did and I bought Symantec Encryption Desktop 10.4.1 MP2 HF2 [Build 824]
However, the PGP Viewer does not work and now tech support says it's not supported for 10.12.6 and they have to do more research.
Symantec should refund my money or else provide a free update of Symantec Encryption Desktop 10.4.1 MP2 HF2 [Build 824] that runs with Mac OS 10.12.6 or better yet, that runs with the latest Mac OS (High Sierra OS 10.13.x) which has been out since the fall of 2017 !!!!!