@davejadco-com, glad it’s working. I can’t imagine why the Mayfly wouldn’t receive an upload without the RTC battery. Or with it upside down, for that matter. I had a student insert several the wrong way and we fried the Mayfly RTC, so double check that.
You can test this by manually set the RTC, disconnect from a power source (USB or lipo battery connected to one of the JST pins), and then reconnect and see what time shows up when you open the serial monitor. I use the PCsync.ino sketch when I have to set the RTC manually.