SSIS PrimeOutput Error?
I had a similar issue loading data and as in your case found the error too general so I checked the option to "Include Step Output in History" which can be found on the Advanced Options of the SQL Server Job Step. This helped me tremendously since the error was a lot more helpful and helped me determine that the problem was on the source. Hope that helps you debug.
I received this error because a flat file with no column names was received, but the import job expected the first row to have column names. Once the column names were added, the error was resolved.
There may be error messages posted before this with more information about the failure.
Did you look for other more specific error messages?
Are you logging errors or steps as they run? If so did you look in the logging table? If you aren't logging in you SSIS package, I'd set that up as part of this fix, it will make it immeasurably earier to find the problem.
Things I would consider: schema changes, permissions changes, any recent software, operating systems updates to the servers involved, data mismatches (the first time perhaps that the Oracle table held data that couldn't be inserted into the SQL table - check columns that don;t directly match first, string data that might get truncated, dates stored as strings that need to convert to datetime, etc.).