Mailing program fails on minimum USPS envelope settings

[soulmanscorner7]

Trying to mail small paper items via USPS, usually set at 9x6x1" envelope, giving low cost of $2.11 thru Ebay to USPS, but when item sells, program fails to allow that low cost, goes to $4.02 via Ground Advantage, costing more to mail than customer pays. Cannot access it after sale is done! Need to get thru to Ebay IT or whatever to make it work properly!

[nobody*s_perfect]

It's not exactly a "fail."  eBay allows sellers to select calculated shipping for "Large envelope" when they set up listings, even though eBay does not sell postage labels for that service.  You have to go to the PO or just use stamps.  That price of $2.11 is the correct postage cost for a 4-ounce Large envelope (formally known as First Class flats).

"Large envelope" is not the same as the eBay "Standard envelope" which is available for selected categories such as trading cards.

[ebooksdiva]

You offer three shipping choices for your buyer to select from. If your buyer chose First Class letter that service only requires postage stamps.

You can't purchase a label on line through eBay nor USPS because there isn't tracking for that type of postage.

That is why you dont see the option to select First Class Letter when printing labels. 

[slippinjimmy]

A 1 inch thick envelope does not qualify for ANY Lettermail service.

[nobody*s_perfect]

That's true: The maximum thickness for a flat is 3/4 inch.

My interpretation of the OP is that he entered 1 inch as a default rather than as the actual envelope thickness.  For instance, he recently sold a ticket stub listed with postage cost of $2.11.  If he's willing to mail it as a flat, which lacks tracking, then IMHO he might as well check on whether it's thin enough to be mailed as a letter, at a fraction of the cost, i.e., if it's not over 1/4 inch thick as shown in your image.