I have been having an issue with shipping quotes randomly not being calculated.

We are unable to find a USPS shipping quote suitable for your mailing address and the shipping methods we typically use.
If you prefer to use USPS as your shipping method, please contact us for assistance.
(Please check that your Zip Code is entered correctly.)

The weird thing is if you keep clicking on the checkout button the quote will eventually come up.

My Zencat version is v1.5.6

I had debug on and when shipping quote come through all the info shows. When the shipping quote is not calculated the message reads (You
can turn off this debug email by editing your USPS module settings in
the admin
area of your store.)

Any ideas would be greatly apprecaited