Hello,
Thank you for your purchase.
Please update the plugin to v2.1.2 – as I just released this new version which adds support for the Twitter v2 API for posting to Twitter.
After you updated the plugin, please go to the plugin’s ‘Main Settings’ menu -> set the ‘Twitter API Version to Use’ settings field to v2
Also, add in the ‘Twitter Access Token’ and ‘Twitter Access Token Secret’ settings fields your Twitter Access Token and Access Token Secret. You can get them, like in this screenshot (indicated by the second arrow, from the bottom part of the screenshot): https://i0.wp.com/artisansweb.net/wp-content/uploads/2017/02/twitter-api-keys.png?resize=1018%2C638&ssl=1
Be sure to add ‘Read and Write’ permissions to the Access Token you create.