You may need to check permissions on the main Lightroom folder or possibly "Run As administrator"
This link has some more information:
I don't know about you guys, but I am sick and tired of being used as a guinea pig to fix crappy beta products that manufacturers have sold me.
Windows 10 and Adobe products have wasted more of my time in the last month than all the viruses and adware I have ever had to deal with in almost 20 years.
This is getting ridiculous. I've been forced into the role of fixing bad products that aren't ready for sale.
Sometimes Lightroom will play a video, other times it freezes trying to play that very same video. I have been using LR to organize videos as well as photos. Now suddenly it is completely unusable.