Return to the H.E.L.M. to speak with Queen Mara Sov.
The weapon refuses your claim. A defensive security measure was triggered as you tried to take the Scepter. Queen Mara Sov may have a solution. She tells you to clear away Xivu Arath's minions from her borders while she prepares a Noble Seal to bypass the Scepter's security screen.
"That is unfortunate. It seems the vault's security protocols have been engaged." —Queen Mara Sov