I finally got my HEM hardware V1 working today. I thought I would briefly document here (for posterity) what worked for me–in case this is of help to others in the future.
After checking and re-checking my HEM hardware V1 clamps, I decided there must be something wrong with the clamps or something wrong with the hardware that reads the signal from the clamps. So I contacted the place I purchased my HEM V1 from and obtained a replacement.
I setup the new replacement HEM V1 the exact same way that I had setup the old one. I did my best to follow the guidance here on the orientation of the clamps (e.g., K->L, L->K)–it’s not entirely clear to me whether this matters but I followed it as best as I could ensuring they were oriented in opposite directions. This time when I turned it all back on it worked!
I had upgraded the firmware to version 3.67, which as I understand it is the most recent. Unfortunately, all of the data was reflecting very high readings so I decided to downgrade to firmware version 3.64 and that worked for me–after the downgrade the data seems reasonable.
Thanks again to @johnconstantelo for writing and maintaining this ST device handler!