I was going to start a new thread on this as this just happened to me but now I know I'm not alone and also that there's probably little I can do except wait 4 days.
I've had 2FA for awhile now and have never had an issue with it. I made a booking yesterday that I wanted to change today and got that same message:
Your passcode cannot be sent since you recently changed the email address and phone number(s) associated with this account.
I called Marriott and what the agent told me made no sense. She said that yesterday I selected that I get the 2FA code via text and that I had previously selected to have it sent via email. I almost always use a browser on my desktop computer so it's just easier for me to have it sent via email so I can do a quick copy-paste. But I guess yesterday I chose send it by text to my phone. I was able to log in and make my booking yesterday. So she told me this "change" of having the code sent by text instead of email is considered the same as a phone number or email address change, which is ludicrous. So now she said I have to wait the 4 days.
I then asked her what will happen after 4 days if I log in and choose to have the code sent via email. She told me I'll be locked out again for another 4 days!
This can't possibly be right. The system gives us the choice of how the site will send us the code for 2FA so that can't be why I got locked out but that's what she told me. I asked her again 3 or 4 times because it just seemed so ridiculous to me.
The other thing is that everything still works on my phone. I'm able to see my account and make bookings.
I guess I'll see what happens 4 days from now but this is utterly ridiculous to me.