Hi there, welcome to Mendix! It looks like your security and/or user targeting aren’t quite set up correctly just yet.
If you are using Studio Pro, I recommend you to check out our how-to guide on setting up a simple workflow here. In case you are using Studio, please have a look at the properties of a user task here, specifically the sections User Assignment and Permissions.
Also make sure you enable the correct user roles in the Visible For property of the page that is linked to your user task.
Hope this helps, good luck and please let us know if you have follow-up questions.