I had a listen and what we've got here is Db major with a flattened 7th -- Db mixolydian which is a mode of Gb major.
The riff at the start uses eb - f - gb - ab - bb - cb in various combinations which is six notes from Eb aeolian (also a mode of Gb) -- the only note missing from the riff is Db so this has an Eb aeolian feel. Eb minor (the relative minor of Gb) is kind of a special key because Eb minor pentatonic is all the black keys on a piano -- think
Superstition by Stevie Wonder.

If we take what you thought the chords were -- Gbmaj Ebmin Bmaj -- B is not in Db. Actually in Eb minor its Cb, but don't worry about that, just think 'B' if you want. Db is five flats, Gb is six flats.
You may be hearing the loop start in a different place from me -- I think it goes (roughly) Ebm7 Bbm7 Abm7 Bmaj7 (B6/9 is also good here).
Then a piano comes in and it's slightly different, then it changes and goes Cm7 Am7 Fm7 quick Bb9 (maybe sus?) -- this is not in any key. So why does it work? Well, the root movement is strong and outlines an F major arpeggio, and there is a common tone (C) in all those chords.