Midi devices showing on audio midi setup but no function when testing

I have two midi devices connected to my computer. One of which (m-audio key station mini 32) used to work fine with logic pro. I don't know if it was a system update or some other problem but the m-audio keyboard stopped working, so I decided to pick up a USB-Midi cable so that I could use my Yamaha keyboard as a midi controller - incase it was the key station that was defective. Both devices now show in the midi studio but when I test them there is no data signal coming from either device. Any suggestions? Is there a possible defect with the Macs midi hardware/software?

Thanks,

Matt