@Domas-Vileikis okay..... that's strange as heck.....
that's not where i expected that failure to occur.
however i do know what the cause is. and i can help you fix it.
the error occurs trying to load the configuration settings for the forum in order to get the CSRF token to log in. this is done by loading
/api/config on your forum.
so, for example, if you were running a bot for this forum the value you would have put in core.forum would be
https://community.nodebb.org and so the configuration would be at https://community.nodebb.org/api/config
can you check to make sure that when you visit the URL in your configuration for
core.forum you arrive at your forum's home page and that when loading
/api/config relative to that URL in the manner i described above your browser loads a JSON document.
if one or both of these manual checks fail then the value you put in the configuration for
core.forum is incorrect and needs to be updated. if both checks pass when tried in a browser then it is most likely your forum has some sort of security in place that is preventing sockbot's user agent access to the REST API of the forum. you will need to update the firewall rules in this case to allow sockbot access, or if you are not the administrator of the webserver your forum runs on you will need to ask your server admin to update the firewall rules for you.
hoping this gets you off and running with sockbot,