unfortunately, you have not provided further details about Version etc. But not to be "empty-handed" I'll Show you that there are some sources of error:
1. Maybe you have to activate/deactivate, so please have a look there:
2, Sometimes, we know in the meantime, the "opm.db file" is the culprit. In this case you should delete it.
3. Did you already try "uninstalling and re-installing"?
Be careful with (de)installing aso. by (de)installing by your own resources. As much as I regret it and as strange as it may seem I fear it's a challenge for Adobe's Creative Cloud Cleaner Tool.
Sometimes - for whatever reasons - CC doesn't "want" to work. In this case you should CC completely delete and reinstall by help of Adobe Creative Cloud Cleaner Tool. (A try to uninstall by own resources is not enough!)
I quote: ... helps resolve installation problems for Adobe Creative Cloud and Adobe Creative Suite (CS3-CS6) applications. The tool removes installation records for prerelease installations of Creative Cloud or Creative Suite applications. It does not affect existing installations of previous versions of Creative Cloud or Creative Suite applications.
Please use: http://helpx.adobe.com/creative-suite/kb/cs5-cleaner-tool-installation-problems.html and follow the prescribed sequence of operations