Thank you for your response and diagram.
I took my machine into the shop and the manager, another employee and myself all stitched on two pieces of quilting cotton with 40 wt Aurifil thread. At first when the manager was sewing, the machine hummed along with no error message. Then when I sewed I got the error message repeatedly. Then the other employee (the store educator) sewed and got the error message and the manager then got the error message. They tried rethreading the machine and looked over everything but could not come to any fix.
The manager is going to talk with the tech people for the store and a tech person at Janome. He took a picture of the error message and the machine. Another employee joined the conversation and they asked if I had the machine plugged into a power strip, which I do and suggested that the power strip might be failing. They asked when the machine was updated and I told them last September. They suggested that it might be a software problem. So we will see where this gets me.