Did you try Aggiegrl's trick listed below ... It was the only way for me to find my 12 digit code. I don't know if it will work on IE, but it does work on Chrome and Firefox
I found another way to find the 12 digit number without calling.
Login to the Disney website.
On the My Disney Experience tab, click "My Itinerary"
Scroll the calendar to your check in day.
Now, use your web browser's "view source" feature to see the webpage's code. I use Chrome, so it is under the top menu View>Developer>View Source.
Once you have the source code open, do a page search for "reservationNumber"
You should see the 12 digit code on the same line in this format:
"reservationNumber" value="44XXXXXXXXXX">
Also, make sure you have the EXACT name on the reservation. I couldn't get my mother's room to work until I realized she was listed as First Middle Last on the mailed invoice we received. On the MDE pages, she is just listed as First Last.