Best way to refresh a Dataset

When attempting a scheduled refresh, is the error message the exact same as the one in the link you posted? If so, have you tried the accepted solution there?

Like yourself, I also have a Postgres DB in AWS and in my experience the gateway config tends to be the root of the problems, but sometimes a gateway is not needed if all your data sources are in the cloud. In these cases, disabling the gateway can fix the issues.

When a gateway is necessary, you can try installing the on-prem Gateway on your own PC and configuring the PBI Service refreshes through there just to test if it works, because if it does then you have determined that the problem is with the AWS gateway.