SQL API - how to create new regular API key for tables created with another regular key?

[Maxim Pokrovsky]

I am running open-source instance installed over AWS, Ubuntu.

Several datasets are created via SQL API programmatically using regular key with write permissions. 

Now I need to issue new read-only API key for using with another application.

On API keys page I get 'Validation failed: Grants can only grant table permissions you have' message. 

Auth API with both master and regular keys also failed. With regular key it returned 401 

Unauthorized, with master key - 403 Forbidden.

What I am doing wrong? Could it be any improper settings and which one?

Thank you!