On All my Mac's is the shortcut ctrl-shift-h woking for a headless access for HDR merge... just my new Mac Pro is not able..
can anybody help?
Do Help > System Info on your new computer. If it's not running CC 2015.7 / 6.7, you need to update to the latest version: Keeping Lightroom Up-to-Date
A bug with the Ctrl + Shift + H shortcut was fixed in CC 2015.5.1: Lightroom CC 2015.5/6.5: Can't merge to HDR from collapsed stacks. | Photoshop Family Customer Community
If this doesn't address your issue, please report which language you're running LR in, whether you are invoking the shortcut on a stack, whether the stack is collapsed or not, and what in detail happens when you invoke the shortcut.