Sadly it would seem that Google is neglecting this particular part of their Google Calendar software. Several of our users have been struggling with issues regarding their calendar not synchronizing properly into Google Calendar beyond their first attempt. Google Calendar very lazily fetches information and doesn't provide a method by which to force it to update your feed. So users are stuck with waiting several days for their Google Calendar to update, with no guarantee that it ever will. I personally really like Google, but their neglect of this particular aspect of the software would lead me to suggest to our users that they look into another Calendar application that doesn't rely on Google Calendar's lazy syncing.
Google is surely aware of this issue, but doesn't seem to be interested in fixing it. There is a feature request that has been sitting in Google's Product Forums since early 2010 and has gained nearly 200 posts with over 10k views... yet Google has taken no action on this issue and likely won't in the near future. You're welcome to read and participate in the forum here: Feature Request: Manual Refresh of external calendar URL / .ics / iCal feeds (external link). Because we have no control over what Google does with their software, we cannot fix or provide support for this issue. You're welcome to add your Unit's Calendar to Google Calendar, but we're unable to resolve any issues related to errors or delays that you may encounter after doing so. Thank you for understanding.
Below is the original guide that we provided for importing your Calendar into Google Calendar.
How It Works
If your scouting organization uses a public calendar, then you can link it to your personal Google Calendar so that all scouting events will automatically appear on your personal calendar. Setting it up is easy and anyone can do it.
First, Get the URL of Your Unit's Event Feed
Go to ⚙ (Gear Icon) > Edit Troop Settings > Calendar Integration tab and press "Generate"
Click the share badge, select "Latest Content" and scroll down to the bottom. You should see a link to your unit's calendar feed, as shown below. If you don't see it, your unit is not sharing the calendar publicly and you'll need to talk to your scouting leaders first.
Copy the url of your calendar feed.
Add your feed to Google Calendar
Follow the steps shown below to add your unit's calendar.
Paste the URL you copied earlier into the box that appears and click "Add to Calendar". Google will now import all your unit's events to your calendar and
keep it synced up.