Update (Sep 24th): I am sorry but there is no ETA yet to resolve this problem. Microsoft is working with Facebook to return this functionality ASAP (Source here). I have also removed the Facebook Pages – Basic Analysis template app from AppSource until this issue is resolved.

Update (Sep 9th): The root cause for this issue is outside of the Power Query connector code and will not require any update of Power BI Desktop or modification of logic in any report file. Microsoft initiated a verification process with Facebook, once this will be done, all the reports will work again. There is no ETA at this stage. To reproduce the problem follow the official Microsoft article here.
Yesterday night (Sep 6th) Power BI Facebook connector started to return errors when used to import public facebook pages. If you are using my Facebook Pages – Basic Analysis template app from AppSource, or have any of my Power BI facebook reports, you will have this error when refreshing your report on public Facebook pages:
DataSource.Error: Facebook: (#10) To use ‘Page Public Content Access’, your use of this endpoint must be reviewed and approved by Facebook.

The error will also occur if you use the Facebook connector to import data from Facebook pages, a technique that I have published in my book and on the blog.
Here is an example of the M code that will return the error:
Facebook.Graph("https://graph.facebook.com/v3.1/MicrosoftBI")
I am sorry for the inconvenience. This may be a result of a bug by Facebook or due to a policy change by the Facebook platform. It can be resolved once the Microsoft team go through an app review and get an approval for the Power BI Facebook app on the Facebook developer platform to get access to public pages. I have opened a ticket with Microsoft and notified the product team and they have started working on this issue.
Please stay tuned.
Hi,
any news?
Not yet. Sorry. No ETA from a Microsoft as well.
Hi Gil, its been almost 2 months now, do you know is Microsoft doing something? Howcome there is no ETA yet?
I am sorry. The review process is managed by Facebook and Microsoft could not share any ETA.