Marriott responded to my ticket with email saying:

"Thank you for contacting Marriott indicating your inability to receive the password reset then log back into your membership.

After reviewing your membership activity, I found a portion of your profile was updated on October 5, 2023. We care about your Account security, so the password reset will not process until 5 business days after the changes made to your profile. "

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I replied that it's not an "inability" to receive password reset, and in fact I did receive the password reset link and did successfully reset my password -- with Marriott system giving me a message about successful password change. I also got a followup email from Marriott "Your password has been changed."
So it's not an issue of inability to receive password reset link, or inability to change password.

This Marriott message that "a portion of your profile was updated,.. the password reset will not process until 5 business days after" just doesn't sound right. So if anyone tried to change any part of the profile, your account can be locked out for 5 business days?!?

When I called Marriott the second time, the Marriott rep confirmed that I did not change my email or phone number. The one thing I remember changing was my default credit card number. I had changed it before, but Marriott continued to show my old CC number as default. So on Oct. 5 when I was making two new bookings, both times it was showing me the old CC number and both times I put in the new CC number, and specifically clicked to make it my new default CC. With all these problems in Marriott system, I'm not sure if the new CC got saved at all.

Anyway, at least this Marriott email response to the ticket, is saying my account is locked for 5 business days before the system will process my password reset, because of a profile change.