scope definition for side_conversation api call with outh 2.0

I have an issue with Api call for side_conversations and scope definition in header. 
I’m trying to  take json for tickets using:
https://{domain}/api/v2/tickets/{ticket_id}/side_conversations Token request: scope requested = 'side_conversations:read', HTTP 200 Token response body: { "access_token": "<masked, fingerprint=36c17344>", "token_type": "bearer", "expires_in": 1799 }

but I’m getting: 403 - {"error":{"code":"InvalidScopes","title":"Cannot access this resource","message":"Missing one of the following required scopes: side_conversations:read,read","allowed_scopes":["side_conversations:read","read"]}}

I tried also scopes: “read”, “tickets:read” and without scope in header.
All examples failed. 
There is no error for example for comments endpoint where url is similar. 

I can run with no error : /api/v2/tickets/side_conversations/events?start_time={start_time}, but jsons don’t contains all fields.

How to define scope to run my api call with bearer token without error?