RS-232 4-Channel DPDT Relay Controller problem

Hardware
1

We ordered 3 RS-232 4-Channel DPDT Relay Controller with Serial Interface

We encountered a problem with 2 of them in our testing. (The 1 other working well)

We trying to connect with no success and without the ability to toggle the Relay’s.

Do you familiar with that problem?

2

Hi,

It’s unusual for two of the boards to not work.

I believe you’re referencing this product: https://store.ncd.io/product/rs-232-4-channel-dpdt-relay-controller-with-serial-interface/

Are you using this with a USB adapter?
Are the jumper settings the same for all three devices?
When the non functioning devices are connected do they display as a serial port?
If you are using it with a USB adapter can you check that the PC/MAC jumper is set to MAC?