Does the fact that a live instructor is not available during the online course change the taxability of the pre-recorded video, even if course participants can ask an instructor questions via email during or following the online course?

No. Although participants can email questions to an instructor during or following the online course, which is a non-taxable component of this transaction, the true object of this transaction is access to a specified digital product. Therefore, the pre-recorded video remains subject to sales tax.