Sorry for answering in English because we're not offering technical support with other languages.
When I checked your account, it seems your data plan is 'Subscription'. For this plan, you should equip at least one paid item to use all mudfish nodes.
I mean I have bablance, but I cant equip(buy) any item :(
Could you please try it again? I think you don't have enough balance to equip one paid item. :-)