Currently, there’s a known issue with Facebook periodically disconnecting accounts that should not be disconnected. They are working on this bug, but have not shared a timeline on when it will be fixed. In the meantime, please try this workaround and let us know if you’re still having problems.
Example of what you should see. Notice the 'deprecated' account on the left.
2) Click Add Page/Group
3) On the subaccounts page, there will be a profile account branch with the account name and one with a "deprecated-" prefix. Ignore these profiles!
Under the profile account branch with the proper account name, select the subaccounts to connect. Don't worry if it says it's already connected to parent account. Scroll down and click 'Connect Selected Pages/Accounts'.
4) On the main accounts page, confirm that the subaccounts have switched over to newly refreshed FB account. The FB account with the "deprecated-" prefix should not have any connected pages, groups, or Instagram profiles!
5) If you have any Instagram business profiles connected to the deprecated account, click the 'Add Instagram' button, then follow the steps to add those business profiles under the newly refreshed account.
6) Delete the "deprecated-" account. Please confirm that there are no pages, groups, or Instagram profiles connected to the "deprecated" account!
Please let us know how it goes, and feel free to reach out with any other questions.