This is a known bug in Lightroom.
Check Don't show again, and then click Open anyway, and the image will open in Photoshop.
Thanks for the response Per.
Yes, the image will open in Photoshop, but the CAMERA RAW plug-in is not available. Error message: The command "Camera RAW Filter" is not available.
I am attempting to combine images using HDR Pro 32bit
As a stand alone RAW file the CAMERA RAW plug-in works normally.
The Camera Raw filter can no longer be used with 32 bit images. This is not a bug but was a conscious decision by Adobe which is explained in the link below, along with some workrounds
Thank you Dave! Though I disagree with the Adobe decision, I suppose I'm powerless...