On December 31st, 2018 Facebook is going to switch from app-level permission for subscription broadcasts to page specific permission.
If you use subscription broadcasts, even using third-party software, and want to continue to use these then we highly recommend you apply as soon as possible so you have time to go through Facebook's review process. This must be done for every Facebook page you want to have this permission.
Page admins may access the subscription messaging request form by doing the following:
In the form, the Page admin will be asked to provide the following:
Give examples of updates you would give to your customers that are non-promotional. Examples might be industry trends, blog posts that aren't just about a new product, or similar.
Please let us know if you have any questions. You can also read Facebook's official information on this change.