Prometheus remote write to cortex returns 405 #4191

I have just recently adopted cortex so apologies if the question comes across as a very basic one.

I have deployed the cortex helm chart (https://github.com/cortexproject/cortex-helm-chart) to our EKS cluster with some changes to the values file.

To summarise,

• auth_enabled is false
• In nginx I am setting some header values
  setHeaders: X-Scope-OrgID: 0 X-Prometheus-Remote-Write-Version: 0.1.0
• At the prometheus end I am setting up the remoteWrite url as follows
  remoteWrite: - url: http://cortex.dev.XXXXX.com/api/v1/push
• Cortex nginx forwards the request to the cortex distributor which returns a 405

Am I missing something here? I would be really grateful If someone would provide some pointers on how to proceed from here.

Thanks.