All backups failing after SQL Server upgrade. Could not load the DLL xpSLS.dll (4309848)

After upgrading the SQL Server instance from 2008 R2 SPX to 2014 all backups jobs have been failing with the following error:  

Error: Code: 0xC002F210 Source: Fast Compression Backups Execute SQL Task Description: Executing the query "execute master..xp_slssqlmaint N'-BkUpMedia DISK -..." failed with the following error: "Could not load the DLL xpSLS.dll, or one of the DLLs it references. Reason: 126(The specified module could not be found.).". End Error DTExec: The package execution returned DTSER_FAILURE (1). Started: 8:00:00 PM Finished: 8:00:09 PM Elapsed: 8.968 seconds. The package execution failed. The step failed.