Yeah...I had that problem too.No app would install or update. Kept getting that message even after factory reset.
I had to remove my main google account from the phone completely. Add a new google account. Then let Google Playstore update, Then add my main google account back.
Don't know why. But this fixed it.
Thanks for the response, I tried that but no luck, the new account had the same issue when trying to update Google Play. removed the old account still and readded it to no avail.
I guess a system reset might be the only alternative.
Sorry--Wrong error message. that's the fix when you can't download anything.
Error -24 is a conflict with the destination folder on your phone. You get it when you are updating or downloading apps you had installed before. Its funny, because I had this problem just today downloading WebMD. I couldn't install it from the Play Store or from an APK file. Since my APK file wouldnt work I knew it wasnt a problem with Google Play Store. So clearing the cache wouldn't work.
Resetting the phone will work. Or if you phone is rooted you can delete the app file in the Data folder.
I had to go to use Root Browser and go to Home--Data-->Data--> find the app file for WebMD and delete it.
I found the issue after a factory reset. As a work phone we have Airwatch installed and a recent update caused the -26 error to occur. I have to un enroll, install apps or updates, and then enroll again at the moment.