Boolean Union keeps failing!

[maimun2002]

I’m trying to boolean these objects with the ring but it keeps failing.
Please Help!

agnostic3.3dm (3.7 MB)

[velopl (Lukasz Domagala)]

You had duplicated objects and some naked surfaces on top.
_SelDup and then Boolean Union works just fine
agnostic3.3dm (1.4 MB)

[maimun2002]

Thank you very much!