It can happen that the backup button for the manual backup is grayed out in iTunes. This can happen if you use third-party software under Windows to manage your Apple devices. This happens because the software changes a variable in order to be able to create iPhone backups itself.

There are two solutions for this.

Solution 1:

1. Close iTunes
2. Launch the alternative Apple software
3. Close the alternative Apple software again
4. Launch iTunes again

The backup button in iTunes should no longer be grayed out. However, if this is still the case, the second solution will help.

Solution 2:

1. Close iTunes
2. Go to Start and type „Run“ or press „CTRL+R“
3. Now enter „cmd“
4. Right-click on „cmd“ and say „Run as administrator“
5. Now enter the following: „%ProgramFiles%\iTunes\iTunes.exe“ /setPrefInt DeviceBackupsDisabled 0
6. Press „Enter“
7. Restart the computer if necessary and then open iTunes again.
   
   The backup button in iTunes is only available for use again.