Keep getting "invalid authentication" error when casting Calendar on any Dashboard to Google Nest Hub

Keep getting this error when casting Calendar on any Dashboard to Google Nest Hub. Anyone have any ideas why? Home Assistant is running on Docker on a Synology 923+. Calendars work when accessing Home Assistant on a PC, and on Companion App, but not when casting (using DashCast) to my Google Nest Hub. Please advise. Thank you in advance!

(Blurred out parts are my Public IP address)