I'm in the same boat. Long time user and this is the worst so far...

I have Xfinity Norton as well and have been fighting this same install issue. The Norton provider shouldn't be the root cause if it is updated from Norton...

PGM tech support had me d/l install package to UltraPak drive I purchased. Seemed to work until I transferred .sty files to that drive and now back to Norton eating the dllelastiquePro3.dll which appears to want to glue all this together. Norton thinks there is a ws.reputation.1 file hiding in there so deletes it.

I've scanned and re-scanned every drive to make sure there is no malware.

This doesn't make much sense.....The Xfinifty Norton causing the problem? Won't run without it and I'm not paying for a separate Norton or shutting Norton on and off everytime I want to use BIAB. And why would an .sty file cause Norton to freak out?
Not pleased with the whole adventure this time around. And tech saying that Norton doesn't like our files isn't a resolution.