[✔] - Capital?

can some senior answer this for me, please? i play Noway and my capital is Christiana, but after a battle,Sweeden had captured my capital,then i fight back and take Christiana back, but it's no longer a capital because the capital building was detroy.So i decided to build a new capital in Lulea (this province used to be own by sweeden) but i captured it.But after the capital building in Lulea is done.i point in every other province-the result is-
"no capital-40,i don't know why?do i have to rebuild the new capital in the same place Christiana,so would it call " capital"?