So I took Mecca and Al Jawf from the Hafzids and I didn't have Admin points to core both, coring Al Jawf and waiting for my Admin points to come back up before coring the other one. I later forgot about coring Mecca, and started converting it to Orthodox which took a few years, and during that time, my claim on it expired. Once it had converted, I tried coring it, but now the Core button is greyed out. Is that because my claim expired? Is it because I'm at war with the Hafzids again, and can only core during peacetime. Will I need to sell Mecca back to the Hafzids, fabricate a claim and reconquer it?
On a different topic, does it make sense to build trade improvements outside of the Trade zone of my capital? Would I just be benefitting some other country with the trade I'm sending their way?
You can't be fighting a nation with a core in the province if you want to core it. It will also freeze coring progress during such wars until you end them, then resume.