AWS Postgres: 'The remote certificate is invalid'

What worked for me (10 min solution):

I had Postgre DB I was trying to connect to, and because is Postgre connection for some reason in Power BI problematic to connect to and was always ending on the same error as yours did, I tried to connect to the same DB via Rest API (JSON) instead and that worked.

1. Install Zappysys Data Gateway - download 30 days trial here 
2. In Zappysys:
   Data Source tab -> Add ->
   Data Source name = whatever you like to call your connection
   Connector type = Native - ZappySys JSON driver
  -> OK
In next window leave everything as it is, and put your Rest API URL, for ex. https://prod.tralala.whoho.dev/sales
and then bit lower in Settings tab use for HTTP request method = GET

Click on Test connection, it should work.

3. search in your Win search panel for ODBC Data Sources (you should have that already installed with your Power BI installation automatically)
4. in ODBC:
 Click on Add -> scroll the whole way down for ZappySys JSON driver -> Finish ->
Data Source Name = whatever you like to call your connection, for. ex. MyEvilPostgre connection -> OK
5. in Power BI
Get data -> ODBC -> choose from the list your connection from ODBC, in our ex. MyEvilPostgre connection. -> OK

6. celebrate after days of torture that your evil connection is finally working