Similar issue. I have both 32bit and 64bit Photoshop CC 2015. 32bit because of legacy plugins. they cannot share the same preferences file since the most recent update. Keep getting messages about missing java script files etc. So delete preferences file and run 64bit version and all is ok (with that one but not the 32bit) It seems to be the new Start Screen that is the root of the issue.
But whenever I choose edit in external app from Lightroom the 32bit version tries to open. As far as I'm aware there is no way to edit the default app. Can work around by having 64bit already running (and it's quicker this way) but should not be happening.
Only seems to be a problem since the last update. I think will leave it until 2016 is released and then drop 32bit. In meantime keep 64bit Photoshop running.
Makes no difference to me whether it's tiff or NEF - always 32bit opening unless 64bit is running. In fact it seems to can default to any previous version of Photoshop if it already running when you choose Edit In.
I still have CS6; CC; CC2014 installed x32 and x64 for each. They all still work ok.
By the way I'm using Windows. Don't know if Mac is affected by this.
It does not work for me to have CC2015 already running. It still opens CS6.
I did a chat session w/ Adobe Support. Only solution was to uninstall CS6 and delete it.
You have to go to Edit/Preferences/External Editing. Go to Aditional External Editor and Choose. You will need to point it to Adobe Photoshop CC 2015's location and execution file on your computer.
I don't use a Mac but in Windows it's fairly easy. Go to a Photoshop CC icon and right click on it. In Windows 10 you will get a choice of More, and hovering over that gets you OPEN FILE LOCATION. This gives you the shortcut to Photoshop CC. Right click again, choose Properties and you will see the location of the file. It will look something like "C:\Program Files\Adobe Photoshop CC 2015\Photoshop.exe". Don't include the quotation marks.
Copy that and paste it into the box for the external editor. It should work if you got the right file and location.
Thanks, Yes, I know I can do that, but it ties up the additional editor which may be needed for other uses.
Right at the top of the box it states "Edit in Adobe Photoshop CC 2015" Doesn't state which one, and that option cannot be altered, unless the path is stated somewhere in the registry.
Why that statement should make it default to the 32bit version is beyond me, and I have deleted the Lightroom Preferences file to see if that fixed it - it didn't
64bit Lightroom is installed by the way.
I would uninstall the 32bit Photoshop because its useless since the introduction of the Start Screen. But that might foul up Lightroom altogether if it can't find Photoshop.
I'm going to have a delve through the registry, may find something. If not just keep 64bit running and it will load. And wait for CC 2016.
Ok bit the bullet and removed cc2015 x 32. It now defaults to CC2014.
So have 2015 x64 running before loading Lightroom and all is ok.
Don't think there is another way. If there's anything in the registry it's very well hidden.
I am having the exact same issue with my MAC running Yosemite. Choosing run copy with LR adjustments will cause it to open in CC2015 or raw file, but edit original will cause PS6 to open. I have set the external editors for both psd and tiff to be CC2015, and I have even reset LR Preferences at start up, and still have same issue. And after improperly loading the PSD file in CS6, and quitting immediately, then may cause a warning exclamation on the thumbnail stating a conflict in settings and the LR catalog.