I've been training in Trailhead for four days and everytime I complete a challenge it will not mark me completed. Simply saying that the challenge has not been completed. (see screenshot) I've had my administrator check my progess and the challenges are completed. We've looked into switching playgrounds, going between lightening and classic along with double checking my login and passwords. Still no luck. This is just one example. 

Trailhead Check Challenge Button is not responding back with results.