App store is completely blank on MacOS catalina
If you open the utilities folder, open terminal.
Type AssetCacheLocatorUtil and look over the output. There will be a lot. Check the IP address and for any errors.
Then, you might make a brand new user account and check that.
Lastly, the machine needs to be on a network with time server to set the clock and access Apple servers. If you have firewall, slow network, blocked network, this program can get stuck and unable to render any information.