In case of two or more purchase scenarios configured for Online Store, one asking for accepting Terms&Conditions and the other one not, it is not possible to finish the purchase, if the T&C screen in skipped before switching to another purchase scenario screens.
A software-related issue PBA-83995: Impossible to accept Terms and Conditions after switching to a purchase scenario without T&C
It is necessary to accept the Terms&Condition on the corresponding screen, when asked. Otherwise, the cart items should be removed and the purchase started anew.
Contact your Technical Account Manager or PTA (firstname.lastname@example.org) to get the status of the issue.