I'm a little puzzled by corporations, more specifically how to start one.
I have a couple of the techs researched that allow corporations (including corporation.) I've saved up a couple of each of the great people, and put them in my capital.
But...none of the people are able to build a corporation. I have all the raw materials available, and no one else has built them.
For instance: I'd like to build Civilized Jewelers. I have a Great Artist saved up, have researched corporation and mass media, and I have 6 gold mines, 10 silver mines, and 2 gem mines (only one of which I need, apparently, at least hopefully. any which way, the point is, I've got them.) Nobody else has built it. But the Great Artist is unable to make the Jewelers.
Why?

You can't be in State property.

Or In mercantilism if you don't have the 3.17 patch

You must also have at least one resource the Corp requires

@monarch1st

Do you have Mass Media Tech which allows Civilized Jewelers Corp? You say you have Corp and 'a couple of techs' but you don't say if you have Mass Media. If you do have Mass Media, then it is probably what Genv [FP] has said that you are in SP or you are in Merc without the 3.17 patch.

Googly and nbcman - a small flame to you both for not reading the original post properly. The OP said clearly that (a) he has suitable reources, and (b) he has Mass Media.

You have to have cash on hand to start the branch office in another city--usually about 100:gold:

Assuming that (A) you have the required resources (as you say), (B) You have researched the required techs (Mass Media, as you say have), (C) You're not currently running the State Property civic, and (D) You have the required Great Person (in this case Great Artist for Civ Jewelers), you need to select the Great Artist and there will be an icon in his icon bar (the same place where you have the icon to start a Golden Age, become a Super Specialist, create a Great Work, etc.) for founding Civ Jewelers. Simply click on this icon and the Great Artist will create the headquarters for CIv Jewelers in whatever city he is currently in.
Any questions?

You cannot found competing corps in the same city. - No Jewellers and Mining Inc in the same place, found the jewellers in another city

Playshogi: you don't need any gold to found a corp - just to spread it.

@ bushface

The original post was edited. The original post read that he had corporation and a couple of the corporation techs. monarch1st clarified what techs that he had has since my posting on Sep 2nd.