In my experience of these things, they tend to either work or they don't. The fact that you've got flashing lights on it once, suggest it is working.

I've only ever used this (mines an Asanté MicroAsanté Print) to hook up a printer on the LocalTalk side with the ethernet side hooked into a small ethernet hub, which the other ethernet macs hook into. If you have such a hub you might try doing something similar. I'm just wondering if plugging it straight into a Macs ethernet port might require an ethernet crossover cable, but putting a hub in between might get round that.

I think it's worth trying.