So that is of course about right, because it is encrypted ! (TWRP is also not quite competent for the situation, but it will work in the correct sequence ! )
Should you wish to recover the phone
(and I quite understand how infuriating the Samsung / USA situation is)
you have backed up, so you are not worried about loosing data,
so (even if the tutorial at first sight, seems not exactly your subject)
this is a well illustrated tutorial on how to “fresh start” and hopefully resolve the encryption issue.