Facebook has changed the behavior of the "follower_count" field for Instagram Insights in Graph API v9+:
With API version 9.0+, follower_count values now align more closely with their corresponding values displayed in the Instagram app. In addition, follower_count now returns a maximum of 30 days of data instead of 2 years. This change will be applied to all other versions on May 4, 2021.
We are planning to upgrade to Graph API v10 for the Instagram Insights data source on March 17th, 2021. This means that our field "New followers", which uses follower_count, will no longer be queryable for date ranges beyond the last 30 days.
After March 17th, users will see the following error if they try to request data for "New followers" outside of 30 days:
"New followers" metric only supports querying data for the last 30 days, excluding the current day
You can make adjustments now to limit queries that use "New followers" to last 30 days or less, to prevent disruptions on the day of the change.
This update should also fix the discrepancy issues we are seeing with that field as the calculation has changed but the older API doesn't reflect that.
Note: this change does not impact the Instagram Public Data source, as it does not use this version of follower_count.