App Store is empty

If you can't connect to the App Store, iTunes Store, or other Apple services - Apple Support describes the applicable steps to follow.

Needless to say, if you are using any non-Apple "anti-virus", "cleaning", or "Internet security" products including "banking security", anything at all in that broad category of utterly useless garbage, don't. A lot of things won't work if you do.

MacOS 13.7.4

I assume you mean macOS 11.7.4.

I noticed a similar question a while ago: Mac OS 11.3.7 cannot connect to app store - Apple Community, in which you described a common bug affecting Big Sur. If Software Update is stuck at "Checking for updates..." with no end in sight, it may or may not be related to the inability to connect to the Mac App Store.

Several workarounds have been reported for that bug, such as restarting your Mac in "Safe Mode" and checking for updates while in that mode, and / or resetting NVRAM. Try both.

How to use safe mode on your Mac - Apple Support

Reset NVRAM on your Mac - Apple Support

After exhausting everything that has been suggested so far, the conclusion of that Apple Support document states "If you tried all of the above steps and you still can't connect, contact Apple Support."