I suppose you meant Panzer Corps and not Panzer General.
I've just checked, and after login, "My Page" has all my games with the serials registered.
Have you registered your games in "My Page"?
Anyway, if you need your serial back, you'll have to write with your order details to info@slitherine.co.uk and ask for your serial.
Don't think I have my order form stuff that was a year ago, when it first came
I cant figure out tho why my game serials aren't showing up. Unless my IP address is buggered up some how.