Hey there.. I've been using Photoshop/Bridge/ ACR for 7 years now but from memory I have had this issue before when installing.
My laptop just got a new hard drive and fan and I've had to reinstall everything.
I downloaded 3 different ACR plugins and none of them have enabled Camera Raw reading for bridge.
I'm using CS6 with Canon 5dmk2 cr2 files.
I have tried 7.1
I have tried 6.7
I've tried this link
and I've tried a Microsoft codec pack somebody else suggested
The 5D2 only needs ACR 5.2 or newer so your current version of ACR 7.1 should open the files.
If ACR isn’t enabled in Bridge then the usual thing is to launch Photoshop and open a raw file at least once without using Bridge, with File / Open or PS / Open.
Doing Help / Updates from PS should install the latest ACR version for you in case that helps.
You can also try installing ACR manually.
If you have a newer OS like Windows 7+ or OSX 10.8+ then try ACR 8.8 is what you want to install:
If you have an older OS like Windows Vista or OSX 10.6.8 then ACR 8.3 is what you want an installer further down on this page: