iPhone 8 not recognized by Finder on IOS Catalina

Finder recognizes the iPhone for a second or two then disappears. I've tried three different cables, two different USB ports on my iMac, relaunched the Finder, on the Sidebar preference I unchecked and rechecked the Finder preference to show the CD, DVD, and ios device in Catalina, the computer and iPhone were both shutdown and then started. How can I get my iPhone to show on the Finder's sidebar so I can save playlist created on my iMac to the iPhone?