iPhone asks for passcode multiple times during backup to Mac

Aa you would expect, you shouldn't need to enter the iPhone passcode more than once. You are probably seeing this because the connection between the two devices is lost during backup.

Try using another USB-C cable or another port on your Mac.

If you use an antivirus or other non-Apple optimization software, try to deactivate them as they may interfere with the backup.

A good way to check if third-party software is interfering is by starting your Mac in safe mode: Start up your Mac in safe mode - Apple Support (SA). Safe mode prevents third-party software to be loaded at start up.

bob7 wrote:

The USB C cable is made by Apple, and when I get this dialog, the battery is showing as charging, so it doesn't seem like a physical connection has been lost.

An iPhone charging successfully does not necessarily mean that the cable can also transfer data. Charging and data transfer are two different functions, and a cable may support charging while failing to establish a data connection.

If the cable is the original Apple-supplied cable that came with your iPhone, it could be damaged or faulty, even if it still charges the device. Try connecting your iPhone using another known-good, data-capable cable and check whether the computer recognises it.

There are two types of cables: one designed solely for charging, and another that both charges and enables data transfer.

Search for accessories that have completed MFi certification. Once an accessory has completed MFi certification requirements and is reported to Apple as sold/distributed, it will be searchable in our public database of authorized Lightning, headset, charging, iAP-enabled, and Find My network-enabled accessories.

Learn how to identify counterfeit or uncertified Lightning-based accessories.

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Excellent points about cables, including the part about the cable needing to be able to xfer data.

While the cable I'm currently using is made by Apple, it is about 6' long, and has a smooth surface.

I have at least one Apple MLL82AM/A "240W USB-C Charge Cable (2 m) … charge cable is made with a woven design … ideal for charging, syncing, and transferring data … It supports charging of up to 240 watts and transfers data at USB 2 rates." I will get that cable from its current remote location and try. I'll also try different USB 2 ports on my MacBook Pro: 14" M3 Pro. I have three ports on my computer that accept USB 2 cables:

From: "System Information":

I don't know if the three busses are equal in capabilities/specs.

--

All that said, I did some testing:

When I connect my phone and enter my iPhone password (to trust my computer), the macOS Finder window for the iPhone sometimes/often displays and comes to the foreground (in any case, the iPhone shows as mounted). I usually switch to a different app, (but don't close that Finder window). Today, I kept the iPhone Finder window in focus (active, with all other apps/windows in the background). I watched a backup complete successfully, and verified that by checking: "Manage Backups…". The fact that I kept the iPhone Finder window in focus most likely has no bearing on anything (because a backup should not require that), but I thought I'd mention it.

I did not get any subsequent request to enter my passcode. This could be purely coincidental. I'll keep an eye out on things.

Question: If you connect (via USB) your iPhone to your Mac and a backup is performed, if you leave your iPhone physically connected, will you be prompted to make subsequent backup(s)?