I have a Ring Pro 2, the systems appears to work fine and when I “Ring System Status” it shows “All Systems Operational”. However, when I check the “Device Health Report” the Transformer Voltage Fluctuates between 15V (poor) and 16V (good). I changed the transformer (24VAC 40VA AC Tra) and I still get this reading is this normal or is there a problem with the system?
Hi @hmb4atc. Have you noticed any performance concerns with the Doorbell? Or is it only saying that there is poor voltage in the Ring App occasionally? If you are experiencing any sort of performance concerns, I would suggest contacting our support team directly so they can take a look and ensure there are no safety concerns. You can give our support team a call at one of the numbers available here. 
It’s only saying poor voltage in the Ring App occasionally, the device works fine.
Hi there, @hmb4atc! It certainly looks like you are using an appropriate transformer and power rating for this to work as intended. While having a proper transformer is a major step, there are some other factors that can be considered with wiring and power loss.
Check out this Hardwiring Checklist for the Video Doorbell Pro, that I put together based off of steps that work often for me. I hope this helps you as well! 
I have the same issue and I am using Ring’s transformer. It works fine, but for a long time it told me that package detection was not available due to the low voltage. They must have fixed something because it allowed me to activate package detection recently.