The SQL statement should be:
EXEC ? = [dbo].[ProcessPingErrorAlert_KeyValue] ?, ?, ?, ?, ? OUTPUT .
Then edit SQL task and choose, in Parameter Mapping, @IsAlert as Output (check pic just for reference, variables are different). The first question mark is just for the return value (you have to declare that variable amd in Parameter Mapping).
Please respect the order you have your question marks and its correspondence by 0, 1, 2, ...
For further information you can try to read this:
https://sqlserverrider.wordpress.com/2014/08/31/execute-stored-procedure-with-input-and-output-parameters-and-return-status-in-ssis/