I would start with what Bee Jay said, but here are a few other details that might help.
I bought a 1x1midi tab
Is that the E-MU Xmidi 1x1 Tab? Then my understanding is that no drivers are provided, and you don't need to install anything.
I think that unit has two or three lights to indicate power and signal. Does a power light go on when you attach it to the computer? Do the signal lights flash when you play the PC88?
Your PC88 was built a number of years ago. Have you owned it for a while, or did you just get it? Does it behave normally in other ways, as far as you can tell? It's possible that it needs a factory reset. This is something you can do easily. Do you understand how to do this?
Do you have another midi keyboard you can use to test the cable? Maybe a friend has a small keyboard you can borrow?
Do you know how to use the Logic Caps Lock keyboard? When you use the Caps Lock keyboard, do you see midi traffic indicated in the Logic Transport bar? It's good to verify that you understand how to do this.