Some of my folders are greyed out in my Macbook Pro, please help.

I'm using a Macbook Pro running on Sequoia 15.6.1 with 280GB of available disk space. Recently, I deleted folders from my Lightroom Classic (8.5.1) and later observed that the same set of folders are not available for review anymore. The same folders are now greyed out, I might be wrong but as far as I've googled, Lightroom catalog has no link to external HDD ( using a Seagate 4TB ). Also, when I'm trying to look for the file by number, I'm hearing the copy paste sound but the file isn't being copied. Please help, I'm a total naive at this technical thing and feeling trapped with this issue lately.