Hi!
I had the same problem and @bonk gave advice that helped me.
He said, "until TTax fixes this, the only way around it is to go into forms and manually enter 100% into 8829 Part II item B so the program can accurately calculate simplified office in home."
I opened the forms by clicking on the top right, found form 8829 under schedule C in the table that appears on the left, and entered 100% for use of my office. Then you click "step by step" at the top right part of your screen to return to the prompt format. I hope this helps you too.
