Curve and Supercard

Has anyone used the Curve or Travelex Supercard in the USA recently?
I had the old trial version of the Supercard last year and it worked a treat and saved me loads of money.
We're currently in the US and I'm having lots of transactions declined on both cards. I've checked with MBNA (my VS black visa is linked to these cards) and there is no problem that end.
Shame as both cards seem to be a good way of earning miles without FX fees.
Would be interested if anyone has had the same issues?
I had the old trial version of the Supercard last year and it worked a treat and saved me loads of money.
We're currently in the US and I'm having lots of transactions declined on both cards. I've checked with MBNA (my VS black visa is linked to these cards) and there is no problem that end.
Shame as both cards seem to be a good way of earning miles without FX fees.
Would be interested if anyone has had the same issues?