Hi Judy, Currently photos will be resized to a maximum of 4000px on the longest side. Make sure you go to Help > My Account in the top right menu and change your Image Quality settings to Archival in order to take advantage of this maximum size. Alternatively when you load the photo, click Undo straight away and it will resize it to the 4000px max.
Hi Wiregirl12, When you first open the image, click undo straight away and the image will return to its full resolution. Alternatively go to Help > My Account in the top right menu and change your Image Quality settings to Archival (before opening the image). Either way you will be able to save at 3872 x 2592. Hope this helps and please let us know if you are still having an issue.