Today Facebook/Instagram has been rolling out a patch and we can confirm all weekly and 28 day values showing correct numbers again. At quintly we have been re-running all historic imports to refresh numbers and all data is complete again. Thanks a lot for your patience on this!
Sadly there is still no fix or work-around available. The topic got more attention by other developers facing the same issue. We hope to see a resolution by Facebook/Instagram this week.
Instagram is currently facing a bug returning zero values for weekly and monthly (28 day) intervals for all page-level Insights metrics of Instagram profiles (e.g. Impressions, Reach). This does not affect daily intervals. There is actually not a lot we can do on our side as there are no work-arounds available. The bug seems to be very fresh and there is already an open bug report with Facebook at https://developers.facebook.com/support/bugs/1098756200558522/ . We hope to see a response very soon.
For quintly this affects data source instagramInsights. As we do update values of the last 30 days in a rolling window fashion with every import, this currently affects all reports based on page-level Instagram Insights data with values showing zero for the last 30 days (e.g. affecting months November and December 2020 for a monthly interval).