How can I get Calendly to check for conflicts with subscribed Google Calendars (including Proton Calendar)?

Hi,

I'm trying to connect multiple calendars to Calendly so that it can check for scheduling conflicts.

I've successfully connected my Google Calendar. However, I also have other calendars subscribed to through Google Calendar, which appear under the 'Other calendars' section. These don't appear as options when I try to select which calendars Calendly should check for conflicts.

In particular, I have a Proton Calendar that I've subscribed to through Google Calendar, and I'd like Calendly to check this for conflicts too. Unfortunately, there doesn't seem to be an option to connect Proton Calendar directly.

Is there a way to get Calendly to check for conflicts across all the calendars visible in Google Calendar, including subscribed calendars?

Any advice would be greatly appreciated!

Many thanks