An Azure service that provides a platform-managed, scalable, and highly available application delivery controller as a service.
"The parameter is incorrect" at the moment you create the connection usually means the gateway or the data source details are not what the service expects, rather than a network fault, so the checks below are the order I would run them in.
The usual causes, in the order I check them. First, the gateway is installed in personal mode; Power Apps and Power Automate need standard mode (personal mode is Power BI only). Second, the gateway build is old: update it to the current release on the gateway machine and restart the service, because the connector and the gateway negotiate parameters and an old build fails exactly like this. Third, the machine the gateway runs on went to sleep or was restarted without the service coming back; put it on a machine that stays on and check the service after every Windows update. Fourth, the SQL login: the connection uses the credentials saved on the gateway data source, not the app user's, and if that login's password expired every user sees the failure at once. Fifth, the SQL Server Browser service is off and the connection string uses an instance name without a port; use server,port instead.
Licensing while you are there: SQL Server is a premium connector and the gateway needs a premium licence, so every user of the app needs Power Apps Premium (NZ$32.40 per user per month on the NZ list, September 2026). If only a few people use the app, pay-as-you-go at USD 10 per active user per app is cheaper for a single app.