Gravity Industries locked out of Instagram account

Not sure if it's relevant/allowed to post an account lockout help request on HN, but here's the text from their facebook post (I have nothing to do with GI; figured someone here might know what to do):

> We’ve been unable to access our Instagram account (@TakeOnGravity) for some days now

> The backup email associated with the account is not one we recognise, nor have access to, presumably belonging to a PR agency from the past. A third level of security that is currently being triggered, beyond password & code-to-mobile, is holding us hostage. It was triggered we think by our HQ (and hence home IP address) relocation.

> We have tried everything with over a dozen Meta-Verifed support people, who have now told us they have given up!!!! Does anyone here have contacts at Meta, Facebook or Instagram who could assist us urgently?

UPDATE

They got back in: https://www.facebook.com/photo.php?fbid=797933975707474