I have a client, based in the US, that uses USPS shipping only for international shipments so none of the "Domestic Rates" are checked. Running USPS (USPS RateV4 Intl RateV2 - March 28, 2018 Version K10) on Zen Cart 1.5.5e.
When a domestic customer enters the checkout process, the following message is received for the USPS quotes:
-2147221202 - The element 'RateV4Request' has incomplete content. List of possible elements expected: 'RateClientType, Package'.
The USPS log shows the following for the RESPONSE from USPS:
<?xml version="1.0" encoding="UTF-8"?>
<Error><Number>-2147221202</Number><Source>Common:XmlParse</Source>
<Description>The element 'RateV4Request' has incomplete content. List of possible elements expected: 'RateClientType, Package'.</Description><HelpFile/><HelpContext/></Error>
with SENT TO USPS:
<RateV4Request USERID="xxxxxxx">
<Revision>2</Revision>
</RateV4Request>