Lightroom problems AGAIN and again

I have the same problem since over a month. I've download Lightroom through creative cloud, I'm paying for it every month and yet I cannot use it comfortably. Every time when I'm closing my computer down and then I'm restarting it my LR is not working. It shows me that "0 days remian" in  "I want to try" option and it asks me to put my serial number. When I'm putting my serial number (the one that is in my profile) it shows me error  and nothing is happening. So I have to delete LR and install it again EVERY TIME WHEN I WANT TO USE IT, which is ridiculous! Is there any other way? When I was asking about it last time someone advice me to "Please refer the article: Use the CC Cleaner Tool to solve installation problems | CC, CS3-CS6 and try installing Lightroom from Creative Cloud Desktop." which I did. It didn't help. Any other ideas?