lightroom 6 won't start on macOS 10.12 when previously OK

[phong.ek]

Lightroom 6 stuck on this starting page. please help

the log from macOS is attached

[AxelMatt]

Try is to reset the preferences to the default settings by following the steps below.

• Close Lightroom.
• Windows: Hold down [Alt]+[Shift] while restarting Lightroom.
  Mac: Hold down [Opt]+[Shift] while restarting Lightroom.
• Overwrite the Preferences when prompted by the dialog.
• Close Lightroom.
• Restart Lightroom.

It's recommended to backup your preferences before you reset the preferences to the default settings: 

https://helpx.adobe.com/lightroom-classic/kb/preference-file-and-other-file-locations.html

If this doesn't help try is to switch off the GPU support from the Lightroom preferences and check if that helps to fix the issue: https://helpx.adobe.com/lightroom-classic/kb/troubleshoot-gpu.html

If Lightroom doesn't start correctly the please see "Solution 2" in the document behind the link below.

Troubleshoot GPU issues | Lightroom Classic (adobe.com)

Another try is to check if there's a .lock file in the folder where the catalog (.lrcat) file resides. If there is a file with the .lock extension delete this file and then try and restart Lightroom.

The Lightroom catalog cannot be opened because another application already has it opened - lrcat.loc...

[phong.ek]

I tried reset preference, and I got this screen instead.

I also tried remove the .lock file.

So far, I still stuck at the screen like in the screenshot above.

[phong.ek · Accepted solution]

Now finally it works. I note what I did below.

I uninstalled Lightroom, and then reinstalled.

During installation, I got "Please connect to internet and try again" error when trying to activate the key (although my Internet connection is fine).

Therefore, I choose to install Lightroom without the serial key ( 7 day trials option ).

Somehow I can login into Lightroom with my adobe account, and I can normally use it now.

Thank you very much everyone for the suggestion and idea.