@Augusto21
Hey there, you can always fight the Raikou, Entei and Suicune guardian once every 12 days as long as you haven't already fought 20 bosses in that week before you fight the guardians themselves. You should have no issues with it.
You also have not caught Suicune, Entei or Raikou yet. Could you take a screenshot of the issue you are facing?