ACH payment processing with AvidXchange

We do our payment processing with AvidXchange. On two occassions, although the ach payments processed, the emails that are send to the vendor did not go. I confirmed this by going to the AvidXchange Self-Managed Print Log. On days when the emails have gone out, I can see a record of the ach payments. On the two days the emails did not go out the payments do not show up in the print log. In my cash register in Netsuite, I do see the entriees being made and have confrimed that the vendors have received their payments. Any idea what's