I don't know why it took me forever to figure this out, but my problem was that my Comcast id was associated with two accounts one of which was my old house. I think that's what account it chose when I logged in as that user. After unsuccessfully trying to get Comcast support to remove the stale account from my user id, the fix for me was to create a new user in the "real" account and log in Roku under that user. Instead of "You haven't purchased anything" there was a guide and actual stuff.
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