serverless create_domain - Failed to create custom domain - amazon-web-services

Question

I am trying to use serverless-domain-manager to deploy serverless to custom domains on AWS but every time I run serverless create_domain I get the generic error "Failed to create custom domain". Here are the steps I've taken and the contents of my yml:
Registered domain on AWS
Set up a hosted zone in route 53
Created a certificate for *.mydomain.com in certificate manager in AWS
Created an iAM user with admin privileges
Run aws configure with iAM user keys
.yml
service: service-name
plugins:
- serverless-apigw-binary
- serverless-apigwy-binary
- serverless-content-encoding
- serverless-api-cloudfront
- serverless-plugin-tracing
- serverless-domain-manager
custom:
apigwBinary:
types:
- 'image/jpeg'
- 'text/html'
- 'text/css'
- 'application/javascript'
- 'application/x-javascript'
- '*/*'
contentEncoding:
minimumCompressionSize: 0
stage: ${opt:stage, self:provider.stage}
domains:
prod: api.mydomain.com
test: api-test.mydomain.com
dev: api-dev.mydomain.com
customDomain:
basePath: ""
domainName: ${self:custom.domains.${self:custom.stage}}
stage: "${self:custom.stage}"
createRoute53Record: true
certificateArn: "cert-arn"
hostedZoneId: "zone-id"
provider:
name: aws
runtime: nodejs12.x
endpointType: regional
region: ap-southeast-2
memorySize: 3008
timeout: 300
tracing: true
iamRoleStatements:
- Effect: 'Allow'
Action:
- 'xray:PutTraceSegments'
- 'xray:PutTelemetryRecords'
- 'lambda:InvokeFunction'
Resource:
- '*'
package:
exclude:
- node_modules/aws-sdk/**
- .vscode/**
- bin/**
- obj/**
functions:
api:
warmup: true
handler: index.handler
events:
- http: ANY /
- http: 'ANY {proxy+}'
Every time I run serverless create_domain I get the same generic error with no extra info.
Thanks

Answer 1

As Erico pointed out you get a bit more info with SLS_DEBUG. It could be that you have an issue with domain certificate and that debug message would tell you that.
In my case it seemed to be a cert problem as it was in a different AWS region so sls create_domain couldn't find it. Overall it's been a rather confusing experience.
Check out the endpointType option:
customDomain:
...
endpointType="regional"
https://github.com/amplify-education/serverless-domain-manager/issues/46
https://aws.amazon.com/about-aws/whats-new/2017/11/amazon-api-gateway-supports-regional-api-endpoints/

Answer 2

In my case, my hosted zone is in another AWS account, so createRoute53Record: true failed to create the route53 record and the hence the generic error.
Changing to createRoute53Record: false fixed the error for me.