This is a bad-data message, which the software really should have caught and explained to you. Without wading through their schema I'm guessing, but it's pointing to something in the Payer Name being misformatted. Make sure you have correctly transcribed everything on that form -- no extra spaces (including at the start or end of the value), punctuation if any exactly as it was given to you, and since we don't know what it's unhappy about I'd say check capitalization and make sure you are not using non-ASCII characters unless you absolutely, positively must (US Government programmers may not have expected Unicode, or even Microsoft's extended-ASCII characters).
If you can't find it, contact the support desk for that tool. And/or see if the XML schemas are public documents and reverse-engineer the error to determine exactly what is expected in that part of the form; without that set of rules for what the program wants to see it's very hard to tell you what it doesn't like.
Sorry; I agree that the question is related to personal finance, but the issue is programming and customer support.
FWIW, what it specifically means is that the XML data is structured something like:
and efile:PayerNameControlText was expected to contain either an efile:CorrectedW2GInd or an efile:CalendarYr, but that was either missing or (possibly) in the wrong place. To say more we'd need to have the XML Schema for this document type, which would tell us what the contents of these are supposed to look like.
Without that, and preferably the document it's complaining about, all we can say is that it looks like there's an error in the information copied from the W2G form, possibly because the section that describes who the employer was and which year this return is for didn't get copied in.
Wish there was more I could do for you, but without access to their programs and your data it's sorta hard to debug this. Which is why you need to take it up with the support folks.