I have noticed an issue with logrotate that may be related to the latest update. This will cause the log folder to fill up. You can see the space used in the Admin screen.
To check, run logrotate…
sudo /usr/sbin/logrotate -v /etc/logrotate.conf
If you see this error near the top…
error: Ignoring 00_defaults because the file owner is wrong (should be root or user with uid 0).
you have the issue.
I think this will fix that issue
sudo chown root:pi /opt/openenergymonitor/EmonScripts/defaults/etc/logrotate.d/*
but your logs may be too full for the rotate to happen.
will tell you how full
/var/log/ is (or from the admin)
sudo du -a /var/log/* | sort -n -r | head -n 30
will tell which is the largest file.
sudo truncate -s 0 /var/log/emoncms/emoncms.log
should fix that, then try running log rotate again and check for errors.