So, I had this same issue after ios17. I have an Iphone 14 Pro and my carplay would connect, but every so often it would disconect with me having to reconnect it. I updated to ios 17.1.2 and my carplay completely stopped working. It wouldn't connect to the Iphone. I reached out to a Apple Representative and these steps helped me to fix my carplay on my 2021 Kia K5:
Try the following steps:
• Forget the stereo from Settings > General > CarPlay > [stereo name].
• Forget the iPhone from the settings (stereo user guide for instructions).
• Rename the iPhone in Settings > General > About > Name.
• Reset network settings on the iPhone.
After doing that:
If your car supports CarPlay with a USB cable, plug your iPhone into the USB port in your car. The USB port might be labeled with a CarPlay icon or a smartphone icon. Be sure to use an Apple Lightning to USB cable.
• If your car supports CarPlay both wirelessly and with a USB cable, plug your iPhone into the USB port in your car. An alert on your iPhone will offer to connect you wirelessly on your next drives.
• If your car supports only wireless CarPlay, press and hold the voice command button on your steering wheel. Make sure that your stereo is in wireless or Bluetooth mode. Then on your iPhone, go to Settings > Wi-Fi, and make sure that Wi-Fi is also turned on. Tap the CarPlay network, and check that Auto-Join is turned on. Then, go to Settings > General > CarPlay, and select your car. Check your car manual for more information.
Hope this helps anyone having issues still within IOS17 or IOS 17.1.2