Hi Diego,
I see that in SM59 the fields "Gateway Host" and "Gateway Service" are empty. In this case each instance will try its local gateway, so of course only the one instance, where the JCo program is registered, will find the registered program.
The solution is simple: in SM59 just enter the same values for gateway host and gateway service that you are using in your JCo program. Then all three instances will know, where JCo is registered, and will find it!
Best Regards, Ulrich