Help! My Catalog deleted from my new macbook, and the iCloud backup keeps corrupting

I'm not sure what you are trying to do. The title mentions a deleted catalog and an iCloud backup. You are not trying to restore your catalog by renaming the lrcat-wal extension, or are you? The catalog.lrcat-wal is not your catalog. It's a helper file.

See: 

https://www.lightroomqueen.com/community/threads/confusing-lrcat-files.33994/

and

https://helpx.adobe.com/lightroom-classic/kb/preference-file-and-other-file-locations---lightroom-6.html

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Hi Sarah,

Sorry to hear about this, it looks like the catalog is corrupt.

Please have a look at a similar discussion here and let us know if it helps: https://www.lightroomqueen.com/community/threads/unable-to-correct-lightroom-cc-corrupted-catalog.31130/

Regards,
Sahil