I enabled USPS global express guaranteed shipping options (there are 4 or them), and none of them show up in my store as a shipping option. I enabled them all at once and then individually and got nothing. I will leave them all enabled while we try to fix this.
. For testing purposes you can make shipping destination Alberta Canada T0A 0A0. And I did try a couple different destinations, emptied cart, refreshed, etc... it really seems to be a cart problem.
alberta, canada T0A 0A0