An error occurs during the process workflow, please forward to your administrator

Please I created a new workflow, I got to send the request to next phase to approval but when I am trying to assign the action in the list to go for the second phase, is appearing the message as below.
Could you guide me please?

In order for an action assignment to work, you need the following:

  • the username belongs to a valid and active user
  • the user belongs to the participant group that handles the action.

Seems like the user is not a member of the participant group, you’ll need to add that user to the participant for the assignment to work.