My college son received a scholarship starting in August of 2020. The systems is saying that I can't claim him his expenses for the first part of the year. Why not?

It depends on when did you pay the expenses for the first part of the year. If you paid it in 2019, you cannot claim it on your 2020 tax return. 

If you paid in 2020, and that amount is not showing in box 1 of the 1098-T;  you claim the tuition credit, based on your own financial records, not the 1098-T. In the 1098-T screen, click on the link "What if this is not what I paid the school" underneath box 1. You will then be able to enter the actual amounts paid.