For me it worked by changing the language of the viewer and also the language in the Marketplace store. In both cases I had to place them in English. The store is working fine for me.
Coincidentally I'm looking for help for the same problem. I haven't been able to post anything new on the Marketplace because I get the following error:
Name in us can't be blank.
https://gyazo.com/fa2f04e413a5aa4e6240a69a0a910f13