Hi @Irakliy I don’t know what is causing the problem with the grasshopper installer script but its worth a try using the pollination grasshopper single click installer, that might have better results
-trevor
I’ll just clarify that the reason for the error is that you have a non-ASCII character in your user name (possibly this Cyrillic character):
Using the free single-click Pollination installer that @TrevorFedyna suggested should solve this for you, enabling you to get the plugin without needing to change your username.