Try the following solutions, in order. After performing each solution, test to see if the issue recurs.
In Lightroom, choose Help > Check For Updates.
Drag the preference file to the Trash (macOS) or Recycling Bin (Windows) and then restart Lightroom. For preference file locations, see:
Uninstall and then install Lightroom again.
For Lightroom, see:
For Lightroom 6 or earlier, see:To determine whether the problem lies with the catalog you’re using, import some images into a new catalog and then restart Lightroom.
Uninstall any Nik Software plug-ins you have installed, including Photoshop plug-ins, and then restart Lightroom. If Lightroom starts, make sure that you're using the most recent version of the Nik plug-ins. For help uninstalling Nik plug-ins, visit Nik Software Support.
Note: Use this solution if you are asked for your serial number after you relaunch Lightroom after getting this error.
The Lightroom folder inside Application Support could have the wrong permissions preventing Lightroom from writing to it, which can cause this error.
Important: (macOS) Apple made the user library folder hidden by default with the release of OS X 10.7. If you need access to files in the hidden library folder to perform Adobe-related troubleshooting, see How to access hidden user library files.
Copy the Lightroom folder into a new user account or other existing account on your computer. Then, restart Lightroom. The Lightroom folder is in the following locations:
Important: (macOS) Apple made the user library folder hidden by default with the release of OS X 10.7. If you need access to files in the hidden library folder to perform Adobe-related troubleshooting, see How to access hidden user library files.
Adobe is researching this issue.
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