Help! Macbook Pro Can't Connect to App Store Purchase And Updates Tab

I bought this macbook pro a couple of weeks ago. I updated it for the first time last week, it went well but now it can't connect to app store anymore specifically on the purchase tab and updates tab. I searched about it online, I tried a few things that are suggested like setting up new location in network preference, checking the certificates but it didn't work. Then I checked the 'about this mac' and i see that my system serial number can't be displayed already. It is found on the system report though. I read and the system serial number which should be found on about this mac will serve as an ID for authenticating connection for app store. How can I fix this? I'm frustrated, can't connect to app store and can't update. Pls. Help!

Screenshot of the issue:

<Image Edited by Host to Remove Serial Number>