Appian Advanced Activity: Using Color in Accessible UX Design

Hello Everyone,

I have encountered I don't know if it is already bug but I have experienced when answering the activity in UI/UX advanced course. I wasn't able to submit the answer when I refresh it I can't go back and retake the activity. Right now I couldn't acquire the certification for this specific course. I'm looking forward to your answer. Thank you in advance. 

On the first image the status is in progress button showed that I can resume but I wasn't able to retake the activity. If anyone experienced this issue I need your help. Thanks.