I see you currently have three Authorized networks and that the usage of your Cloud SQL instance is currently reduced (meaning not a lot of operations currently running). Were you able to add in your new network since the 13th?
From the
graphs I see that your instance usage peaks everyday, which could be the reason for the operation block you experienced. Performing database configuration changes during low traffic is most recommended.
You can always attempt to log into your instance from one of the Authorized Networks, and run the 'show processlist' command to see what operations are running. You can then kill any processes that you think may be causing high resource usage (aka the operation block) and retry your configuration change.