The Origin8 is most likely ISO, or very close to "British" threaded. The fork is most likely Italian. Same diameter, same pitch but different thread profile. I forget but one is 60° and the other has a 55° inclusive angle to the thread profile, and one is slightly rounded the other not.

So… Go Italian, or have the steerer chased with a British threaded die.
Just to be sure its not the headset, find a known English threaded steerer and check the fit of the threaded parts.