So I turned on debugging for the python script. Here's what I got in my log:
2020-07-30 15:26:24 RPINTS: unknown message: SatusCheck;
('Unexpected error:', <class 'serial.serialutil.SerialException'>)
Traceback (most recent call last):
File "/var/www/html/python/FlowMonitor.py", line 270, in...