Very frustrating... This is not specifically related to the beta, this is in the general Sierra 10.12.3 release as well, but it is not fixed in the beta either...
I upgraded several users to Sierra only to find out that they could no longer refresh their subscribed calendars (webcal://) using the "Refresh Calendars" under the View menu, as it was greyed out. After getting so frustrated and wiping everything out with a clean install of Sierra, I see this is the case even on a brand new install, so it has nothing to do with the fact they were upgraded.
It seems "Refresh Calendars" is not available to select UNLESS you have iCloud Calendars turned ON. Well, we don't want that, we don't use that, and I don't want to create iCloud accounts for all the users in the first place. This functionality worked fine in El Capitan, why was it broken in Sierra?
The only way to refresh them is to quit and restart the app!?!? {SIGH}
I am reporitng it here, and maybe will do the same in the General forum, but as far as User/Community forums go, there is nothing we can do, this is plainly an Apple bug. I've had ZERO luck ever fiiling a bug report, so I may try it but am not the least bit optimistic. Apple, you are really going downhill...