Q: iMac can't see iPhone since updating to iOS 9

Hi feathers7,

Thanks for using Apple Support Communities. Based on what you stated, it sounds like the iMac is not seeing the iPhone to use AirDrop with. I would recommend that you read this article, it may be able to help the issue.

Use AirDrop to send files from your Mac to another nearby Mac or iOS device - Apple Support

Cheers

Hey feathers7,

I know you said that this article did not solve the problem, there is one section that that I want to make sure you were able to review. Also make sure to have WiFi and Bluetooth enabled on the iOS device. 

If you don't see the recipient in the AirDrop window or sheet:

• Make sure that both devices have AirDrop turned on and are within 30 feet (9 meters) of each other.
• If you're sending to an iPhone, iPad, or iPod touch: 
   
  • Your Mac needs to be a 2012 or newer model with OS X Yosemite or later.
   
  • The iOS device must have Personal Hotspot turned off in Settings > Cellular. 

Thanks for using Apple Support Communities.
Have a good one

Thank you for using the Apple Support Community. Due to the nature of your issue you may find more information by using another one of Apple's support resources - https://expresslane.apple.com/GetproductgroupList.action