Problems with Nova launcher

[.macbookpro.]

So as soon as I got my Nexus 5, I installed the free version of Nova Launcher. Then, around Christmas time I bought the prime version, and installed it as well, no problems.
Then, my phone had a spasm, and I had to restore from backup all of my apps.
Now. I am unable to install the prime version. I get an "unknown error during installation. '-24'" message whilst in the notification bar it says "installing". I've tried reinstalling both versions, and I've messaged the help email on their google play store page, but au haven't had a response in a month.
So does anyone know now to resolve this problem?

 

[0dev]

Go to Settings > Apps > All > Play Store. Reset the app. Do the same for Google Play Services. Now go to accounts in settings and sign out of your Google account and sign back in again. Finally reboot the phone. That should sort it.

If all that doesn't work, you may need to factory reset the phone. It could be whatever caused the initial problem hasn't been fully resolved.

 

[.macbookpro.]

Go to Settings > Apps > All > Play Store. Reset the app. Do the same for Google Play Services. Now go to accounts in settings and sign out of your Google account and sign back in again. Finally reboot the phone. That should sort it.

If all that doesn't work, you may need to factory reset the phone. It could be whatever caused the initial problem hasn't been fully resolved.

Do you mean Force Stop, Disable, or clear cache?
Thanks for the response!

 

[0dev]

Do you mean Force Stop, Disable, or clear cache?
Thanks for the response!

Force shop then clear cache and clear app data.