upgrade order issue

We have upgraded the nopcommerce from 3.9 to 4.10 we have follow all the upgrade rule 3.9 to 4.0 and then 4.10 and we also change the theme we are facing few issues. On order confirmation order cart is empty but it places the order and giving error "Access to the path 'C:\' is denied. order mail is not receiving.

Check the System > Log for the full error message, and post it here