slack bot scope missing while making api request

For people having this problem in the future;

your integrated bot has full access to the slack api, whereas a bot in a slack app don't, as it will used publicly. When you successfully finish oauth2, you should get 2 tokens, user access token and bot token. The user token is used to read history from any channel/groups, and the bot access token is used to write to them. This means you constantly have to be switching from user token to bot access token in your app.

Also, remember that bot-user MUST be a member of a private channel which you want him to connect to.

Hope that helps.

Ps, if any found a better way going about this, feel free to answer below.

Since you did not mention it: You also need to specify all required scopes on the admin page for your Slack app under "Oauth & Permission Scopes".