Hi there, you need to go back to your twitter api and under the settings tab of your application, scroll down to Application type and select Read and Write. Then at the bottom, click the update button.
Now click on the Rest Keys Tab and reset your application keys.
Next go to the Details Tab, scroll down and click the "recreate my access token" button.
Afterwards copy your new consumer key & secret as well as your new access token key and secret to the update.php file and upload to server.
Add a new product and it should work then.