Second Time Machine drive not recognized at startup

[Sangoma]

I have Time Machine set up with two drives. If I start my Mac and hold the option key, only one of the drives shows as a recovery option. If I remove that drive, the other still does not show up.

I also notice that the same drive that does not show up also does not get the Time Machine icon on the desktop.

According to the Time Machine widget, both drives are participating in the backup just fine.

Any ideas of what is going on?

 

[Sangoma]

Odd. It works fine with Yosemite