Unique Values in Dynamic Down List

Please try at
F17
=IFERROR(INDEX(OffersTable3[Offer],SMALL(IF(FREQUENCY(IF(OffersTable3[Region]=$F$16,MATCH(OffersTable3[Offer],OffersTable3[Offer],)),ROW(OffersTable3)-ROW(A$1)),ROW(OffersTable3)-ROW(A$1)),ROWS(F$17:F17))),"")
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Data Validation list
=OFFSET($F$17,,,COUNTIF($F$17:$F$27,"?*"))