If you are running Nik Collection 6.5 in PhotoLab 7, and you click on Nik and get the message “Nik is not installed on this PC”. I may have a solution for you. If you are running AVG Tuneup, any version over the past 6 months on your Windows 10 PC, it will disable the plugin function 100% of the time. Your individual apps are unaffected, but your plugins will no longer work. You cannot run the Nik installer to correct the problem. The only choice is to delete Nik completely and then reinstall it.
I have had 2 chats and three phone calls, with AVG, allowing them to control my PC. They have seen the behavior, but not one Support person had any idea for a solution, and two had zero idea what they were seeing.
In the end, there’s but one solution, if you want to keep your plugin function, it’s to not install AVG Tuneup on your Windows 10 PC.