Dear @sestech,
in case of failure, (either from ZATCA’s side or your side).
Your system should be re-submitting the XML documents again and again till receiving a response “200, 202,400”
if you are afraid that you will not be ably to comply with the 24 hours rule for the simplified tax invoices, then, you are advised to raise a failure notification from ZATCA’s website.
I hope this clarifies your question.