We'd like to know more. Are you getting any error message while assigning a custom URL? Share more details and screenshot and we'll take a look!
@TeamYouTube I hit 100 subs DAYS ago, and no eligibility for custom URL. Account is far past 3 days old and channel art is uploaded. Starting to feel as though you don’t care about growing creators. 
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Thanks. Twitter will use this to make your timeline better. UndoUndo
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