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Hello There ! would you please check this link Troubleshoot game issues on Xbox | Xbox Support for further help.

However, if the issue persists, your console will need reset in order to refresh the system. Therefore, you will only need to follow the steps mentioned on the link bellow and your issue should be fixed.

How to reset your Xbox console to factory defaults | Xbox Support

All game saves are signed individually to each gamer profile/gamertag. That I know of, game saves cannot be transferred to other gamer profiles/gamertags. You should have insisted not to delete your offline profile, you can't get it back if it isn't an Xbox
LIVE account. Sorry, but yes, this sounds like the technicians fault for telling you to delete an offline non-LIVE profile.

Try deleting her game save and see if it will load yours then. If you are signed in under your profile it should sync your game save though. Can you manually load a game file ?

the "8015190B" is being caused by a Corrupt Gamer Profile on your Xbox Hard Drive. First you are going to have to delete your Profile off of the Hard Drive and then re-recover it. To do that you must be on the Xbox 360 Dashboard > Press the Guide button
on your controller > go to Settings > and select System Settings > Select Storage or Memory > Then select the Drive that the profile is located on > Gamer Profiles > Scroll down to the gamer profile you are having issues with and delete it. When prompted "Delete
profile ONLY." > Then once deleted you need to re-recover the profile, to do this: Press the Xbox Guide button on your controller then Select Sign in, then Download Profile. Enter the Windows Live ID associated with your Xbox LIVE gamertag. Now, enter your
Windows Live ID password. Then save it to your Hard Drive. -Credits of Civiks

have you tried deleting then redownloading your profile ????

1.Go to Settings, and then select System.

2.Select Storage.

3.Select All Devices.

4.Select Gamer Profiles.

5.Select the gamertag that you want to delete.

6.Select Delete.

7.Select one of the following:

◦Select Delete Profile Only. This deletes the profile but leaves saved games and achievements.

◦Select Delete Profile and Items to delete the profile and the associated saved games and achievements.

1.From the Xbox Dashboard, go to social.

2.Select Sign In or Out.

3.Scroll right and select Download profile.

4.Sign out of your account (if you are signed in).

5.Select Download profile.

6.Enter your Microsoft Account username and password.

hope this helps !!!!