My web store (zc 1.5.5f) has been using the USPS Plugin version K8 for over two years without any problems.
Today because a customer asked about it, I noticed that when I put an item in my cart and checked-out, that he was correct, and there was NO QUOTE for Retail Ground rate. When I went to my Admin screen and brought up Shipping Modules, I noticed in RED that There was a newer version of the Plugin.

So I checked the forums and saw that there was a new K10 version released 03-08 of this year. So I downloaded the zip file and unzipped it. Then per instructions in the readme.txt, I REMOVED the old shipping module; renamed the two now-older usps.php files to usps_php.k8; via FTP uploaded the two new usps.php files to respective folders; INSTALLED the USPS shipping module, and filled in all the fields as before. But here is where things went bad !!

I no longer got any USPS price quotes, not even the Priority rates I use to see. Instead I get this message:
-2147221202 - The element 'RateV4Request' has incomplete content. List of possible elements expected: 'RateClientType, Package'.

I tried changing various fields that I had left as default before, but nothing worked, so I decided to go back to the OLD VERSION of USPS Shipping module. So I REMOVED the newer shipping module; renamed the two newer usps.php files to usps_php.k10; and renamed the two older files back to usps.php files to respective folders; INSTALLED the USPS shipping module, and filled in all the fields as before. But I still get the same error message !!

I even turned-on debug mode, with info printed to the screen, and saw nothing of note.
USPS build: 2017-09-16 Server: production Quote Request Rate Type: Retail Quote from main_page: checkout_shipping USPS Options (weight, time): --none-- USPS Domestic Transit Time Calculation Mode: NEW Cart Weight: 0.125 Total Quote Weight: 0.125 Pounds: 0 Ounces: 2 Maximum: 50 Tare Rates: Small/Medium: 0:0 Large: 0:0 Handling method: Box Handling fee Domestic: $0.00 Handling fee International: $0.00 Decimals: 3 Domestic Length: 8.625 Width: 5.375 Height: 1.625 International Length: 9.50 Width: 1.0 Height: 5.50 All Packages are Machinable: False Enable USPS First-Class filter for US shipping: True Sorts the returned quotes: Price-LowToHigh ZipOrigination: 46405 ZipDestination: 13732 City: Apalachin State: New York Order SubTotal: $14.99 Order Total: $14.99 Uninsurable Portion: $0.00 Insurable Value: $14.99
RESPONSE FROM USPS: ================================== -2147221202Common:XmlParse The element 'RateV4Request' has incomplete content. List of possible elements expected: 'RateClientType, Package'.


Finally I called USPS help line 1-800-344-7779 but could not get anyone to help. So figured I would see if anyone here can help. As of now, I have NO USPS Quotes on my web store, since I can't figure out how to even get back to where I was 2 hours ago So if the customer wants to buy the item he asked about, he will have to use UPS shipping which will be too high, and I will probably lose the sale !!