Hello AdmiralESoonShin243,
Thank you for reaching out in Apple Support Communities. We understand you're unable to connect to the App Store on your Mac. We'll be happy to help.
Excellent job with the troubleshooting steps that were performed. It appears you followed the steps outlined in this helpful article: If you can't connect to the App Store, iTunes Store, or other Apple services
To help isolate this behavior further, we recommend to restart your Mac in safe mode. This helps to verify your startup disk, delete some system caches and more. Here's an article with additional details and the proper steps to take: How to use safe mode on your Mac Once the Mac is in safe mode, please restart your Mac as normal and see if you can use the App Store without any issues.
Please keep us posted with the results.
Kind regards.