Online activation and purchase of Windows 10 using PPPOE and MS Store

I have installed a Windows 10 Home using media creation tool from Microsoft. Now I would like to activate it and purchase the valid key. So, I step into Parameters > Activation and select there a Go to Microsoft Store entry. The window with MS store page opens, but when I click on Buy option I get an error code 0x800713AB with a description "Internet Connection required".

Obviously, I am connected to Internet. But I am using a PPPOE connection which is rather good and MS store page can be opened in browser (although price there is different (higher), heh).

If this may be helpful, after boot I am connecting ("dialing") to my connection manually, this is fine for me. Another interesting feature: in Control Panel > Network and Internet I have a "no Internet Access" notice, but everything works fine. I was also able to install some application from MS Store, although got the same error message, but it installed and worked.

So, how do I get past the 0x800713AB error message and purchase the activation key with usage desktop version of Microsoft Store?