Hello Chris, I wonder if this is a similar issue the problem reported by @delphsoft here https://community.openenergymonitor.org/t/myelectric-setup-invalid-response-object-error
Do you see any errors in the emoncms.log view?
Does an EmonPi update and/or restart solve the issue?
Do the input and feed last values appear to update ok?
Under Setup > Administration > Server Information is WriterDaemon running?
Buffer150 feed points pending write
WriterDaemon is running with sleep 60s