EasySMU not working with Linduino

So I've got 3 Linduinos (DC2026) and 8 EasySMUs (DC2591A), and I'm not able to get them to work. They used to work, but not anymore. I've tried all the SMUs, and multiple SMUs on each Linduino. It seems as though the LInduino has trouble communicating with the EasySMU. Here's what I've done so far:

1) Redownloaded and reflashed the EasySMU sketch onto the Linduino. The sketch uploads without any problem.

2) I set the EasySMU to CH0, and with Arduino's serial monitor, I send the command CH0:VOL 1. The serial monitor returns:

3) I then send the command *IDN?, and the serial monitor returns:

It seems as though the Linduino does not detect the EasySMU. I have tried this with multiple EasySMUs and multiple Linduinos. All of them behave the same.