Marketpress - Checkout isn't working

Marketpress - Upfront -

when you hit checkout, it just sits there and spins. never goes anywhere.

Yes, SSL certificate has been installed, and I've tried in SandBox and Live mode... I get nothing. Please note I am having some api issues (https://premium.wpmudev.org/forums/topic/marketpress-api-error-couldnt-resolve-host-productionshippingapiscom#post-1060645)

so not sure if I should continue this on that other thread or if this could be another unrelated issue.