Warner Chappell has confirmed that SECRET's "Madonna" MV being blocked was a mistake.
In a reply to a distressed fan who wanted to know what happened, the company replied,
@puteribalqish10 this is most likely a mistake, have already sent email to dept that handles this, should be corrected in next day or two.— Warner/Chappell (@WarnerChappell) April 2, 2017
It's most likely that their automated system had detected the MV and thought it was a repeat of Madonna's song "Secret". While the MV is still blocked as of now, hopefully the situation clears up soon.