After reading that I could have both the desktop software AND the cloud client on the same machine, I installed a trial version of the cloud Lightroom. Now I cannot launch my fully-licensed desktop software! I uninstalled the trial creative cloud software, and now it's broken.
Help! I have photos to edit!
It's very probably not a good idea to install both on the same machine, and your best bet is to completely uninstall all copied of Lr, if you haven't already done so, then start again.
If you have used your operating system procedure for uninstalling the application it will not interfere with your Catalog, Preferences and personal files.
Download the latest version if you have a LR 5 license key, from the link below.
This should reinstall LR 5.7 and you should be good to go.
After the installation shut down the computer and reboot.