New Lightroom Install cannot open my catalog because "It is too new"??!?!? Help, how to fix this?

In order to use the current version of LR, you need to have Windows 10. Not compatable with windows 8 or below. If you had a previous version installed and you imported images, you could edit and everything, because things would be compatable. You really need to update to Windows 10 to be able to take advantage of LR going forward. Older versions are being eliminated due to copyright infringement agreements and versions below win 10 are not being supported by MS and Adobe will not support versions that are pre win 10. If you don't upgrade OS, you will be left out and no way to support your LR. Once you upgrade, you can import older catalogs and system will update them. Problem in upgrading OS is that your computer may not be powerful enough to support it, which will require new computer (Had that happen to me in past). 

As to your current install problem.

Not at a computer just now (to test). but if I remember correctly, that button that states a Installed, the down symbol to the right, should allow fir a manage pull down, should allow for a install other version. Take a look.

However you might have to uninstall, then manage and install the newer version

P.S. check your computer and see if somehow you have 2 versions installed.

Also, in addition, Windows v8 is largely seen as a huge error by Microsoft. And Adobe absolutly hates it. Apparently a free upgrade to Windows 10 is still possible. Following a bit dated

https://www.digitaltrends.com/computing/how-to-get-windows-10-for-free/

In addition (but not a solution to your issue)

Your copy of the Adobe Creative Cloud Desktop App, is old. You need to update it.

https://helpx.adobe.com/download-install/kb/creative-cloud-desktop-app-download.html

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Hi there,

The version, Lightroom CC 2015 you are currently installing through the Creative cloud is the predecessor to Lightroom Classic. You might have had Lightroom Classic CC version 7.0 or higher installed on the computer which is no longer available for installation through the Creative Cloud. If the catalog you are trying to open was created using the Lightroom Classic CC version 7.x then it would not be compatible with the version you have installed.

Lightroom CC 2015.14 (Lightroom 6.14) and Lightroom Classic version 8.2.1 and above are the versions available for installation through the Creaive cloud now out of which Lightroom Classic is not compatible with Windows 8.1.

Please check: https://helpx.adobe.com/in/lightroom-classic/system-requirements.html

We would request you to upgrade to Windows 10 to install Lightroom Classic.

Regards,

Nikunj