iTunes could not back up iPhone because an error occured

If you successfully backed up your iPhone on the same computer and in iTunes last month but encountered an error message this time, there are several possible reasons for the problem:

• Insufficient disk space on computer: Check if your computer has enough disk space to store the new backup. iTunes backup may take up a lot of space, especially if the data on your phone has increased.

• iTunes Software Error: Although you have updated to the latest version of iTunes, sometimes the software may still encounter errors. You can try to reinstall iTunes to make sure there are no corrupted or missing files causing backup failure.

• Device Connection Problems: Check if there is any problem with the data cable, try to use the original Apple cable or change to a different USB port. Sometimes unstable USB connection may cause backup failure.

• Corrupted or conflicting old backup files: If the last backup file is corrupted or has problems, it may prevent a new backup from being created. You can try to delete the old backup as follows:

1. Open iTunes

2. Click “Edit” > “Preferences” > “Devices” in the menu bar.

3. Find your device backup, click on it, and then select “Delete Backup”.

4. After deleting, try to back up your iPhone again.

• iPhone software issues: Try restarting your iPhone and then try backing up again.

• Permission or firewall issues: Make sure the firewall or security software on your computer is not blocking iTunes from communicating with your device. Sometimes, security software updates may mistake the iTunes backup process as a suspicious operation and prevent it from running.

If none of the above methods can fix the iTunes backup issue, then you have to go for other backup options like iCloud.

These are the references for other backup options:

1. How to back up your iPhone, iPad, and iPod touch - Apple Support
2. How to Backup iPhone/iPad/iPod Touch [All Methods]

With iTunes, you can create multiple backups for the same device, but iTunes typically overwrites the previous backup for that device unless you manually archive the old one.

Check the guide:

Archive iPhone backup in Windows - Apple Community