Connected to salesforce sandbox but no retrive refresh_token

Hi!
I have successfully configured the salesforce sandbox connection, the authorize get the response with the variable “code” into the callback url but the method request_token return false affter click on authorizaion button. In the plugin code I did debug the index ‘refresh_token’ into the request object and it arrives empty.
I do not know how configure the “API (Enable OAuth Settings)” section in Salesforce sandbox pannel, especially the options “Require Secret for Web Server Flow”, “Require Secret for Refresh Token Flow” and “Introspect All Tokens”
Any help is highly appreciated!