Cannot access app store

Hi,

one of our macs will serve another user so I'm cleaning it a bit up and want to update it to el capitan. But the problem is it won't connect to the app store. Very strange because I can connect or the internet, the software update works, but I cannot connect to the app store, nor to iTunes. Very frustrating.

 

How can I check this?

 

@Tomorrow. i just created a new apple ID. When I try to sign in with that account in apple store and itunes store, I won't connect.

 

Update: I created a bootable usb with El Capitan (downloaded from another Mac) and did a clean install. Afterwards I still had problems connecting to the app store. Now, today, I tried to logon inwww.apple.com with safari (to check (again) that my logon is correct) and at once the Mac signaled there were new updates.

Thanks everyone for thinking about this weird problem.

Jvuz