Hi just_giddy,
Thanks for contacting Apple Support Communities!
We understand that you're unable to use the App Store as it doesn't open for you.
If you haven't already, we'd suggest that you start by restarting your Mac: Shut down or restart your Mac - Apple Support
There are several additional steps you can take to help isolate this behavior if restarting doesn't resolve it as outlined here: If you can't connect to the App Store, iTunes Store, or other Apple services - Apple Support
"1. Find out if there’s an outage for a service in your country or region.
Check Apple’s System Status page
2. Make sure that your device is connected to the internet
Use any web browser to connect to any website. If nothing loads, use another device on the same network to see if it can connect to any website. If no other devices can access the internet, turn off your Wi-Fi router, then turn it on again to reset it. If you still can’t connect to your Wi-Fi network, contact your internet provider for more help. If only your first device can’t connect to the internet, get help with Wi-Fi on your iPhone or iPad, Apple Watch, Apple TV, or Mac.
If you use cellular service to connect to the internet on your iPhone or iPad, make sure that you have cellular data turned on for the app that you're using. To do this, open the Settings app, tap Cellular, then turn on Cellular Data.
3. Update your software
Update to the latest version of iOS or iPadOS, macOS, tvOS, watchOS, or software for your non-Apple device. Then try to connect again.
4. Check the date and time
Make sure that the date and time on your device are set correctly for your time zone. If the date and time are incorrect, update them or turn on the option to set date and time automatically.
On your iPhone or iPad: Open the Settings app. Tap General, then tap Date & Time. Get more help with date and time.
On your Mac: Open System Settings, click General, then click Date & Time. Or open System Preferences, then choose Date & Time.
On your Apple TV: Go to Settings > General > Date and Time."
We hope this helps you.
Take care!