Please use the below link to subscribe to our ICS calendar.
Here's a step by step guide on iOS as an example:
Go to Settings> Apps > Calendar.
Tap Accounts > Add Account.
Do one of the following:
Choose a service: Tap a service—for example, iCloud or Microsoft Exchange—then enter your account information.
Add a calendar account: Tap Other, tap Add CalDAV Account, then enter your server and account information.
Subscribe to iCal (.ics) calendars: Tap Other, tap Add Subscribed Calendar, then enter the URL of the .ics file to subscribe to; or import an .ics file from Mail.
URL: https://api.scouting.org/advancements/events/calendar/89798