You didn't say which year you have. If trying what Todd says does not work, try this. Go
2015 and download v.5.0.89 (that is the one I've using forever). If you have a previous version scroll down. Click on the Install file to make sure it is good, but do not install yet.
Go to your C drive and open Program Data, Radium, then Living Cookbook for the latest year. Open the folder and copy the license.xml file to your documents. Open the file to a text file so you can see your license/s. The license will read something like: LC15-0000-xxxx-xxxx-xxxx. If you upgraded, copy the license from the year/s you upgraded. Copy the entire contents of that folder to your Documents folder. Do this even if you have current backup.
Then uninstall LC using Control Board program and features. Restart your computer and then install the version you just downloaded. It should open and ask for your license, etc. You can enter the info or try what I do, which is to got back to Program Data and add the license.xml file (replace the one there if there is one). Go back and open the program and hopefully it will pick up your license.
If you have a super current backup, restore from it. If your backup was not up to date, then replace the the items in the program data folder with the ones you copied, one by one. I rename the one there by adding a 1 and then copy the old one. Do this for every folder. You should be able to open LC again with your recipes, not the standard program. Reads more complicated than it actually is to do. Windows sometimes messes up with the splash screen.
Hope this helps.