Error: Invalid JwtGenerator options. `apiKeyId` is required

If you run the command npm start  and get the following error:
 Invalid JwtGenerator options. apiKeyId is required    

full error code can look like this:

Problem: it means that you didn't put correct APP_KEY_ID into a config.json  file. 

Solution: 

1. check your config.json  file, to be sure you didn't miss to admit API_KEY_ID 
2. Go to your Virgil Dashboard (https://dashboard.virgilsecurity.com/) -> API KEYS section  -> copy necessary API KEY ID (related to your API Private Key) ->

paste your App_Key_ID into your config.json -> save config file -> open CLI and run npm start.