Apple’s iOS 11 introduces new camera formats (HEIF [High Efficiency Image File Format]/HEVC [High Efficiency Video Coding) option which can save your iPhone’s storage space with quite a significant margin (50%), yet giving you the same – if not better – quality (see an article on JPEG vs HEIF comparison).
The problem is that not many apps out there that support the new HEIF (for photos) format yet and many would still prefer files in JPG/JPEG. While Facebook, Twitter, and most photo editing tools can read and process your iOS 11 photos taken in HEIF, other apps like Google Photos can’t yet.
If you try syncing or backing up your iPhone photos in iOS 11 with Google Photos, you’ll get a never ending progress bar and your photos will never get synced across.
In all fairness, iOS 11 is still in Beta, so it’s not really Google’s fault for not supporting the new format yet. However, there is an official tweet saying that it’s in the works – but we are not sure when an update will be released.
We're on it
— David Lieb (@dflieb) June 30, 2017
For now, you have 2 workarounds if you still want Google Photos to work with your iPhone photos on the new iOS 11 Beta:
 For the future, change the Camera settings so that it takes photo in the JPEG Format only like iOS 10 and before.
You can do this by going to Settings->Camera->Formats. Then, under the “Camera Capture” option, change to “Most Compatible”.
The next time you take a photo, it will be stored in JPEG and Google Photos will be able to sync again.
But what about the current photos that you already took in the new format? There’s an easy work around for this:
 Copy your photos from the iPhone to a Computer, and then use a web browser to upload your Photos to Google Photos
The photos in HEIC format will automatically be converted to JPEG on your computer, assuming you have the settings turned on:
Go to Settings->Camera->Formats. Now under the “Transfer to Mac or PC”, change to “Automatic”.
You can then just use your web browser on your machine and upload to photos.google.com.
So, how to make the iOS 11 Photos work with Google Photos again? You either wait til Google updates its app to support the new HEIC/HEVC format, or transfer them to your computer and upload through your web browser.
I’m keeping the HEIC/HEVC formats for now on my iPhone 7 Plus.