Reinstall PS Lightroom 5.7.4

Lightroom 5 Direct Download links:

https://prodesigntools.com/lightroom-5-ddl-comparison-vs-lr4.html

Failing that, you will need a modern Creative Cloud subscription. 

Creative Cloud Photography Plan (approx $10/month for 12 months). Includes the following:
- Photoshop CC and Photoshop on iPad
- Lightroom on desktop, mobile and the web
- Lightroom Classic
- Portfolio website + hosting
- Spark with premium features
- Bridge
- 20 GB cloud storage (upgradable to 1 TB).
https://www.adobe.com/creativecloud/photography.html

Which Operating System do you have now?

Win11 might make this a no-can-do.

https://helpx.adobe.com/download-install/kb/windows-11.html

FIRST Log-in to your Adobe account and click this link https://account.adobe.com/products
--click Order history on the left and then the link to your order that will show on the right
--and finally click the link "Downloads and serial numbers" that will appear
---as always, write the serial number in a text file AND copy that text file and the
---download file(s) to an external drive (or two) to be sure you have what y

OR

I do not know how far back this process will go, but try...
Direct Download Links https://prodesigntools.com/tag/ddl MAY help
-you MUST do what it says in Note: Very Important Instructions
-https://prodesigntools.com/adobe-cc-2015-direct-download-links.html#download-instructions
-the prodesign links go directly to Adobe's file server, so this process will
--only work until Adobe completely removes the old version(s) from the server
.
IF/When you do have a download, be sure to copy it to AT LEAST one external device
-since Adobe does sometimes remove old versions from the server
-a usb flash drive or external hard drive, or write to a DVD
-plus a text file containing your serial number if you have CS6/CS5 or Elements