Elements opened the raw images from my Canon Rebel but wont open the images from my 6D.

CR2 files are different for every Canon model. Same goes for all manufacturers. NEF files are different for every model of Nikon camera and so on. This detail trips up many people.

Raw files are opened by the Camera Raw plugin which is used by Elements when opening Raw files. The Camera Raw plugin must be updated every time a new model of camera is released. So, when you buy a new camera, you inevitably have to update the Camera Raw plugin. Sometimes this also means paying to upgrade Elements because different versions of Elements are compatible with different versions of Camera Raw.

A list of supported cameras, and which version of the Camera Raw plugin is required, is given in the link below.

Cameras supported by Camera Raw

CR2 files from the T2i were first supported in Camera Raw 6.1 which is compatible with Elements 8 onwards.

CR2 files from the 6D were first supported in Camera Raw 7.3 which is compatible with Elements 11 onwards. So you'll never be able to open those CR2 files in Elements 10.

Options:

1. Upgrade to Elements 15 (or buy the new, full version if it's cheaper). You can then edit Raw 6D files in Elements 15, or
2. Download the free DNG converter. Batch convert CR2 files from the 6D to DNG format. You can then edit the DNG files (not the Raw files) in Elements 10. An extra step for you but no extra cost.
   Digital Negative (DNG), Adobe DNG Converter | Adobe Photoshop CC
   DNG is a generic Raw file so there's no loss in quality. You're just working with Raw files in a different form. Convert to DNG is simply an extra step in your workflow every time you shoot new photos. Some people don't mind converting. Others find it painful and prefer to pay to upgrade their software so they can open and edit their Raw files quickly with no extra steps.