The Aramaic version says ‘our God,’ while the Greek says ‘our Lord.’ There’s great uncertainty about which language was used to write Revelation. Even if it were originally in Aramaic, some say that the original was lost, and the Aramaic we have today could be a later translation back into Aramaic from the Greek traslation of the original! We just don’t know.
Whatever really happened, either the original Aramaic or an Aramaic translator understood these words to be referring to Almighty God. The context also supports this, since Jesus is mentioned as a separate person next.
In this instance, our translation goes with the Aramaic and says ‘our God’.