I have been provided a new Serial Number / License by Adobe support. How do I apply it to an installed Lightroom 5.5 that I currently have? I can't get into Develop since the temporary license had expired.
Click on Help menu (on Windows) / Lightroom menu (on Mac) and choose the option to Sign in, then click on License this software if prompted and enter your serial key to activate the program.
If that does not work, kindly let us know the exact message that you see under Develop Module.