Yes, other forum users can see your message.
There are two versions of LR, a cloud-licensed version and a serial-number-licensed version. Uninstall whatever version you have using the normal OS-uninstall process, then download and install the serial-number-licensed version of LR 5.7 from the Adobe Updates page:
This should ask you for a serial number when you start it up.
Or if you have purchased the Creative Cloud Photography Plan that has PS + LR from $10/month then just use Help / Sign-In and login to your Adobe account from within LR.