Thar be your problem. You need to install the ROM and GAPPS then reboot and let all your apps and system setting sync first or else you will get this error. After all that is finished then go back and install your theme.
So unfortunately you will have to wipe your data and cache and reinstall using that sequence.
Np. The incognito series of themes uses a modified phone apk and it doesn't play well with the setup and such (at least that's what I gather the problem is)