PowerApps syntax for connections to internal systems in totally not clear or not documented. Examples:
I have a test SharePoint server on 0365 and can connect to that with PowerApps.
I also have serveral Sharepoint servers on premise that are behind the firewall. When I try to define them as a source it all fails. The main reason is that PowerApps does not explain at all what syntax to use
a) for the fields to fill out or what type of accounts are needed. E.g. The user to connect with does that have to be an end user, an admin, a Sharepoint service account? Is is domain\logon name or just logon name?
b) for the fields when you define the Sharepoint it: Is the SharePoint URL an Internal URL? Does it need https://? It it just the server name or the full URL? If the server has a public URL and an Internal URL will the gateway use the Internal DNS or does Azure solve the DNS (the latter would make things not work)? At any rate, none of this is explained and ZERO examples shown, making us waste hours just trying to guess.
Really Microsoft you can do better, document what is obvious to you and document for the harder cases not just for when everything is the easy version.