We implemented MarketPress on a site we built for a client. They are experiencing intermittent issues when submitting orders to USPS; sometimes it's a "USPS Error: Order Does Not Exist" message, sometimes everything seems to process normally but the amount charged for shipping is $0.00. Most of the time, everything works perfectly.
They are using the calculated shipping option and offer Priority Mail (general option, no specific package sizes are selected), First-Class Mail Metered Letter, and First-Class Mail Parcel.
We have increased the store's timeout limits on our end, but with limited success.
Any suggestions or insights on how we can resolve this for our client?