Putting your suggestions together finally solved the problem.

Pausing the code after sending the command to the device gave time get data from the device. Unfortunately when I tried your suggestion the first time, I did so in the debugger. You then suggested I turn off the debugger but unfortunately by the time I did that, I had removed the lines to pause the code. I finally did both at the same time and now everything is working as expected.

Thanks so much for your help.