Which Camera did you used to take the raw Picture you are Processing in Lightroom?
See Cameras supported by Adobe Camera Raw and ensure that Photoshop Cs6 does Supports Camera raw version required.
Update Photoshop CS6 to Camera raw 9.1.1 following Keeping Photoshop Up-To-Date
The last version of Camera Raw that is compatible with Photoshop CS6 is Camera Raw 9.1.1. There will be no more updates available for Photoshop CS6. That message is telling you that Lightroom has additional changes that your version of Camera Raw might not be able to interpret when you send an image from Lightroom to Photoshop. You are given choices. You can open the image anyway, or you can let Lightroom create a copy that includes all of the Lightroom adjustments and send that copy to Photoshop. In most instances, you would want to make the second choice. When that warning message displays I believe there is a checkbox to indicate not to display it again. The only way you can resolve the problem would be to upgrade to Photoshop CC 2015. Otherwise, just choose the option to edit a copy with Lightroom adjustments.
This is a new error for me. I've been using a Canon 5D Mark III for a while and haven't had any problems, so felt this to be unusual. I've been doing the method suggested "let Lightroom create a copy that includes all of the Lightroom adjustments" and haven't run into any problems with this. But, I just wanted to make sure that there wasn't something that I was missing.
What you are missing is PS CS 6 is using ACR 9.1.1 and LR is using ACR 9.3, IE a Newer version of ACR then what PS is using. That is why you are now getting that message.