In Strategy 2021 Platform Analytics installations, “(Unable to connect to the database, please check your host, port, username, and password.).” error occurs when choosing remote pgsql database whose database name (and schema name) different from platform_analytics_wh as shown below:

(Es kann keine Verbindung zur Datenbank hergestellt warden. Bitte uberprufen Sie Ihre Angaben zu Host, Port, Benutzername und Kennwort.)
ENG: (Unable to connect to the database, please check your host, port, username and password details.)
Note: The current installation GUI doesn’t have the option to enter Database name or schema name.

This is working as designed with Strategy 2021 that there is a hard requirement for the standard schema name to be platform_analytics_wh.
An enhancement request has been raised to have the ability to enter database name and schema name in GUI while installation of Platform Analytics
Strategy will continue to investigate and post updates as soon as they are available.
It is possible to configure Platform Analytics to use a different database as long as the schema is named platform_analytics_wh. Refer to document below on Configure Platform Analytics to Use a Different Repository Database Name.
Configure Platform Analytics to Use a Different Repository Database Name.