Have you subscribed to the creative cloud photography package that includes Photoshop and Lightroom? Or, are you trying to install a standalone version of Lightroom?
I installed stand-alone lightroom.
I brought it about a year ago or less.
My Mac crash so, I need to reinstall it. But this time I have creative cloud installed.
The serial number just does not work.
Do you need my serial number?
No, I'm just a user like yourself, and have no access to any information from Adobe. If I understand you correctly, you have subscribed to the $9.99/month photography program. If that is the case then you need to uninstall any version of Lightroom that you may have installed from a disk or from a download from Adobe. Then install Lightroom from the creative cloud manager. When you do that, Lightroom will be running and your creative cloud license, and it will not require a serial number. Instead, it relies on your Adobe ID and Adobe password.
Thank you very much for your help.
I’ll try that and will let you know so that we can help other if this can solve the issue.