Create SQL Instance fails with "An unknown error occurred." - google-cloud-platform

Question

I'm trying to create a Cloud SQL instance but am unable to do so.
I have tried many variations:
DB: Postgres 9.6 / 11.1, Mysql 5.9
Tier: micro, 1 vcpu / 3.75MiB
Public network (non selected)
Via the console (pictured) or via gcloud
I have an up-to-date billing account (have other GCP services running ok). I am the project owner and logged into the console and gcloud as such
Each time i see the same unhelpful, generic error message "An unknown error occurred.". See below also for an error log example.
{
insertId: "XXX"
logName: "projects/XXXX/logs/cloudaudit.googleapis.com%2Factivity"
protoPayload: {
#type: "type.googleapis.com/google.cloud.audit.AuditLog"
authenticationInfo: {
principalEmail: "XXXX"
}
authorizationInfo: [
0: {
granted: true
permission: "cloudsql.instances.create"
resource: "instances/XXXX"
resourceAttributes: {
}
}
]
methodName: "cloudsql.instances.create"
request: {
#type: "type.googleapis.com/cloudsql.admin.InstancesInsertRequest"
clientIp: "XXXX"
resource: {
backendType: "SECOND_GEN"
databaseVersion: "POSTGRES_11"
instanceName: {
fullProjectId: "XXXX"
instanceId: "XXXX"
}
instanceType: "CLOUDSQL_INSTANCE"
region: "us-central1"
settings: {
activationPolicy: "ALWAYS"
availabilityType: "ZONAL"
backupConfig: {
enabled: true
replicationLogArchivingEnabled: false
specification: "every day 07:00"
}
dataDiskSizeGb: "10"
dataDiskType: "PD_SSD"
ipConfiguration: {
enabled: true
}
locationPreference: {
gceZone: "us-central1-a"
}
maintenanceWindow: {
}
pricingPlan: "PER_USAGE"
storageAutoResize: true
storageAutoResizeLimit: "0"
tier: "db-custom-1-3840"
}
}
}
requestMetadata: {
callerIp: "XXXX"
destinationAttributes: {
}
requestAttributes: {
auth: {
}
time: "2019-06-04T05:46:10.255Z"
}
}
resourceName: "instances/XXXX"
response: {
#type: "type.googleapis.com/cloudsql.admin.InstancesInsertResponse"
}
serviceName: "cloudsql.googleapis.com"
status: {
code: 2
message: "UNKNOWN"
}
}
receiveTimestamp: "2019-06-04T05:46:10.297960113Z"
resource: {
labels: {
database_id: "XXXX"
project_id: "XXXX"
region: "us-central"
}
type: "cloudsql_database"
}
severity: "ERROR"
timestamp: "2019-06-04T05:46:10.250Z"
}

Answer 1

Since as you've said, the error message is too generic, the appropriate course of action, in my mind, is to have the issue digged into deeper by inspecting your project.
As a GCP Support employee I recommend you to open private issue by providing your project number in the following component:
https://issuetracker.google.com/issues/new?component=187202
Once you have it created, please let me know, and I'll start working on it as soon as possible.

Answer 2

I've had a similar issue trying to create a SQL instance using Terraform.
As it turns out, database instance names can't be reused immediately:
If I delete my instance, can I reuse the instance name?
Yes, but not right away. The instance name is unavailable for up to a week before it can be reused.
To solve this I had to add a random suffix to the database instance name upon creation.