This is not Adobe. Rather user to user.
If you do not presently have purchased downloaded installation files specific for Premiere Elements 10 Mac or an installation disc for Premiere Elements 10 Mac, you will need to purchase a new Premiere Elements 10 Mac from whomever has it in stock (that will not be Adobe) or purchase another version.
Keep in mind, when you purchase from a download, you are purchasing installation files specific to the computer operating system to which the files are being downloaded. When you buy the box packaging (which Adobe is not selling), it comes with an installation disc for Windows and another one for Mac.
Please confirm if you original purchase was for Premiere Elements 10 downloaded to a Windows computer?
Please consider and supply more details.
Add On...if you decide to purchase recent version as download from Adobe, you will need to look into upgrade pricing of Adobe. Adobe upgrading is a pricing term only. If you can show proof of purchase of an approved earlier version, you get its lesser price rather than its full price. Adobe upgrade pricing may not be less than those of non Adobe sellers who have their own pricing policy.