are you going to ironclad online? Also is it the case that you cant get past the login?
If so you need to create an Iron clad online account, Im sure theres a create button on the same page as the login page where it asks you for your username and password, so click the create button, that should take you to a web page or some kind of form(cant exactly remember) fill in the form , if it asks for your key you got when you purchased the game enter all that, enter a password, once its done submit the form. Next check your mail not sure if this is necessary, the checking mail but is good practice, if you dont have to do anything else as per mail start the game again, goto iron clad online in game and enter your usernmame and password from the earlier created account and you should get in.
Maybe its the case login isnt your issue but if that is the case that it is not the issue you should provide information regarding the exact steps you took to get online and exactly at which point you cant get no further
Hope you get it sorted
(Sorry all if my login help isnt 100% accurate I only ever signed up for sins once and it worked so its all from memmory .)
edit .......ok apologies you do mention about signup so when you click iron clad online then create account what happens? does any wiondow form to fill in pop up?
It doesnt take you to a web page from what I can see, just pops up a small window in the game window and you put your details in, when you click create that window does it come up asking you for:
It wont work unless you have valid cd key from a stardock store. You most likely have all that but just trying to cover all bases here
will be easier when I know exactly how far you have got.