The shipping rate cannot be determined at this time

Okay...
I went thru all of this forum and all of google to find an answer, but could not.

I installed two modules.
-Zone rates
-Royal mail special delivery (next day) - defined by weight, this is only for zone 1 which is in my case UK...

From admin they are all on and green button is showing.

But when I get to the check out page, i can only see one option for shipment. Instead I get this:
The shipping rate cannot be determined at this time

I need my customers to be able to choose special delivery as well.

How do I enable this?
oh please help.