Appt not showing on provider cal

I am having an issue where App+ only puts the appointment on the "General" calendar and not on the "service provider" calendar on gcal.

I am also getting a few repeat errors under the "logs" tab.

Error calling POST https://www.googleapis.com/calendar/v3/calendars/MYSITE.com_rbogbfllu...8mc417sgc@group.calendar.google.com/events: (400) Invalid attendee email.

Error calling PUT https://www.googleapis.com/calendar/v3/calendars/MYSITE.com_60ma19g6u2o...6s0c0@group.calendar.google.com/events/dbli...h14da5tluh677jc: (404) Not Found

(I changed the domain and truncated the urls in this post)

A little more background: It worked fine until a few weeks ago. I didn't change anything prior to it not working. Each provider still has their same gcal keys etc. Using 2012 theme (no mods), and appt+ version 1.3.1.

Any help would be appreciated. This is an annoying glitch.