iMac 10.9 not receiving MIDI signals from US 144 interface

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I have a new iMac running OSX 10.9. I have a Tascam US-144 interface. I have managed to get this interface to work in Garageband when using electric guitar using the new Tascam driver 3.00d8. The interface control panel works.

I have an old Yamaha PSR-140 MIDI capable synth. I have connected the PSR-140 to the interface. I see the "MIDI In" light on the interface flashing. When I play a few notes on the keyboard the light goes solid while I am playing. The MIDI signals seems to be arriving at the interface.

However I cannot get the MIDI signals to the computer. I installed a program called "MIDI Monitor" to see what was being transmitted to the computer. It shows no signals getting through. However it does show the keyboard I attached to my interface within "Audio MIDI setup" in "MIDI Sources". When I use Garageband and create a piano track, the keyboard doesn't do anything.

I borrowed a UM ONE Mk II MIDI to USB converter and that worked. However why it won't work via my interface and MIDI cables has me beat

In the Apple app "Audio MIDI Setup" I connected the keyboard to the US 144 as per attached image. Seems right to me.

I am at a loss as to why my iMac is not receiving MIDI signals from my keyboard.

 

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I just tried it on a Windows laptop. It works fine.

 

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I've been told by Tascam distributor that Tascam has dropped support for the US144. So it's now a paperweight. Goodbye forever Tascam. How hard could it be to create a driver considering they created one for the similar US144 mkII?