Hi @Craig Knauer ,
Did Sylvia's answer solve your question? To reiterate Windows 10 1909 is unsupported. The Windows 10 1909 ISO is only available to be downloaded from subscription websites such as VLSC (Volume Licensing Service Center). However, VLSC does not support personal customers.
If her answer solved your question please mark this post as answered to help others find the information they need. Thanks!