Did you double-check that you have LR 6.8 / 2015.8 by opening the system information in the help menu?
Lightroom version: CC 2015 
License: Creative Cloud
Operating system: Mac OS 10
Version: 10.12 
Application architecture: x64
no where does it say 6.8
after I updated to 6.8, when i launch LR i notice the intro graphic logo looks different, this is how i presume it did update.
no where in LR does it specifically display or show 2015.8 or 6.8, nor did previous version for that matter.
i tried the patch installer already
it says update failed.
if i install the full trial version it installs, goes thru the whole process but when i launch LR it get a previous version. i dont know where it install the new trial version but i cant find it on my computer, very odd.
when i try to install the update i get same exact error as when i try to install the ACR 9.8 update.
this is the error I get when I try to install that update file you gave me link to.
originally thats what I tried when that failed, i simply downloaded the full version, trial, entered my cdkey, it installed fine no errors.
but as you can see when I launch it, its the previous version but displays the new logo, so bizarre.
and nowhere does it say 6.8, only way to know like you men tioned is to look at system info and read a cryptic version number which means nothing because how to know for sure thats really 6.8 when its a bunch of numbers.
anyways, thanks for the help.
i've asked my friends and they too have exact same error message. what did they do...to get around this....wait for next update as most of my friends find LR to be very buggy like when 6.1 came around and broke everything so their logic is if it dont work just wait for a better version to come around.
i'm a bit more tech savy and I'll try to find out how to fix the problem by asking in forums.
ok i figured it out
you cant delete the file in finder directly
you have to move it to the trash can
once in there you have to:
- Open Terminal. It's located in /Applications/Utilities. ...
- Double-click the Trash icon in the Dock to reveal the contents of the Trash. ...
- Press the Command-A key combination to select all files in the Trash.
- Drag the files from the Trash to the Terminal window. ...
- Press Return. ...
- Empty the Trash.
once i did that i ran the update and it worked.
so removing that adobe file worked, so in fact it was an adobe related issue, damn adobe has so many bugs in their updates.
i will pass this along to my friends.
To check to see if Lightroom CC 2015 is up to date click on the Lightroom menu bar Lightroom "About Lightroom" and you should get this popup screen. See it says 2015.8 Release. and also ACR 9.8. (this means you have Lightroom CC 2015.8 installed which is the equivalent of Adobe Camera Raw 9.8)
To check if the equivalent version of Adobe Camera Raw Plugin is installed in Adobe Photoshop CC check from the menu bar in Photoshop "About Photoshop Plugins" and you should get the screen popup as shown below. Then you will know for sure that both Lightroom and the Adobe Camera Raw Plugin in Photoshop are up to date. If you do not have Adobe Photoshop Installed you cannot install the Adobe Camera Raw Plugin.