You cannot mix the standalone version with the creative cloud version. They are licensed differently. Your creative cloud subscription relies on your Adobe ID and your Adobe password. The standalone version requires a serial number. You will have to uninstall Lightroom and then reinstall from the creative cloud. When Lightroom 5.7.1 was released I wasn't able to install it from the creative cloud application manager until I signed out from the manager and then sign back in again. That is probably what you are going to have to do.
It is sorted.
I have to say that being a long long time user of Adobe, this whole subscription based continuous updates suck a lot more than it should. The amount of bugs on Adobe apps when they get released is depressing.
It's unfortunate that you are having difficulty. I have only been using the creative cloud subscription for a couple of months, but I haven't had a single problem with it. I uninstalled my standalone Lightroom right after I installed the creative cloud application manager. Then I installed Photoshop and Lightroom from the creative cloud manager. The only problem I have seen is that I had to sign out and back in before I could install 5.7.1. Other than that, everything has functioned flawlessly.