Question: Why after upgrading to el Capitan (MAC OSX 10.11.1) is my MAC no longer recognizing the Zoom Mini USB Modem?
Answer: In the first released versions of el Capitan (versions MAC OSX 10.11.1-10.11.3), the Zoom USB Mini Modem was no longer hot swappable. In order for the USB Modem to be recognized by the computer, you must completely power down the MAC PC and have the mini USB modem installed prior to powering the PC up. This cold boot is necessary in order for the MAC to acknowledge the hardware. It is reported that the latest update released March 21, 2016 for el Capitan, MAC version 10.11.4 has fixed this issue and now the USB Modem is again hot swappable. Apple has reported improved stability, security and compatibility for el Capitan with this update. You can download this latest update from https://support.apple.com/kb/DL1868?locale=en_US