help to connect alarm signal driver hbs86h

No need, it should work as is.
Do you have enable wired to your drives?

Yes, they are connected

I have managed to get linuxcnc to stop when an alarm goes off, but the driver does not turn on the red LED, so I will never know which driver is faulty...

Of course, hence my question.
To have it work properly, you need separate inputs for all drives, then LinuxCNC shows what drive faulted.

Yes, I understand you but I don't have input for each driver. I don't care that linuxcnc tells me which driver is wrong. I just need it to come to a stop when that happens.

The problem is that when the driver fails the red LED does not light up. On the other hand, if I disconnect the driver from the bob, the red LED does turn on. I am doing all the tests with a single driver and the only input I have free.

you have to collect signals from all amplifiers via a relay and connect it to one input  of your Bob. As a bonus, I would connect LEDs to show who is in pain.