Does it still have the capital from the previous owner?

In a recent change when you place a governor it places the capital. You can demolish it and relocate it. 

Hey, sorry I didn't see your reply. To send in a bug report just post the details here or even better on Discord. discord.gg/invite/galciv. Discord just makes it easier 

That said depending on the faction it might already have a capital. Things like Father Tree, Mother Hive, etc... are capitals. Likely that is what is going on. 

This is a legit bug.  It happens when you do a culture takeover against some factions.  The capital building is on the building list but you can't place it - though you can place anything else you have access to.  I guarantee there's a bug report about this floating around somewhere as it's easily duplicated once you run into it.

As I said Discord is a non-starter. For me. This is a blank page.

If you don't want to use Discord you'll need to setup an account with something like OneDrive, Google Drive, Dropbox etc... and post the save here then follow the process for the relevant platform to share a link to the save file. 

Thank you. I have forwarded to the siterep channel.