Working with XML Data Providers in Acumatica (Imports)
I'm sharing this because I lost an hour searching for the answer, and trying everything I could think of.
XML Data Provider does NOT do what you think it does. It reads files created specifically for it that include a full data structure at the start.
It has no way of reading the full data structure of your XML file, to use anything like what most systems use for XML packets, you'll need to create custom data providers.
Full help article on this is here:
This answer is 100% in debt to the following Stack Overflow user, without them I would never have found the part of the wiki that details this:
The first time I tried using the XML Data Provider, documentation was not available and I had to decompile it to understand what it did. It's not clear to me if this can be used for anything useful, so I ended up creating my own data provider in C# to use for the different scenarios I had to deal with. It's not that hard and it gives you 100% control over the output.