"Key not valid for use in specified state." - SSIS Package

I have a SSIS package deployed in my server. My database is a SQL Server 2008R2, the SSIS was developed in Data Tools 2008.

It used to work perfectly but since a few days it started to throw this error:

Failed to decrypt protected XML node "DTS:Password" with error 0x8009000B "Key not valid for use in specified state.". You may not be authorized to access this information. This error occurs when there is a cryptographic error. Verify that the correct key is available. End Error Error: 2018-03-27 15:15:37.25 Code: 0xC0016016 Source: Description: Failed to decrypt protected XML node "DTS:Password" with error 0x8009000B "Key not valid for use in specified state.". You may not be authorized to access this information. This error occurs when there is a cryptographic error. Verify that the correct key is available. End Error Error: 2018-03-27 15:15:37.84 Code: 0xC0202009 Source: Package Connection manager "MYDATABASE" Description: SSIS Error Code DTS_E_OLEDBERROR. An OLE DB error has occurred. Error code: 0x80040E4D. An OLE DB record is available. Source: "Microsoft SQL Server Native Client 10.0" Hresult: 0x80040E4D Description: "Login failed for user 'MYUSER'.". End Error Error: 2018-03-27 15:15:37.84 Code: 0xC020801C Source: XX Description: SSIS Error Code DTS_E_CANNOTACQUIRECONNECTIONFROMCONNECTIONMANAGER. The AcquireConnection method call to the connection manager "MYDATABASE" failed with error code 0xC0202009. There may be error messages posted before this with more information on why the AcquireConnection method call failed. End Error Error: 2018-03-27 15:15:37.84 Code: 0xC0047017 Source: Carga criticidad SSIS.Pipeline Description: component "XX" (1) failed validation and returned error code 0xC020801C. Description: One or more component failed validation. End Error Error: 2018-03-27 15:15:37.84 Code: 0xC0024107 Source: XX Description: There were errors during task validation. End Error DTExec: The package execution returned DTSER_FAILURE (1)

I already checked this post: SSIS: Just started getting a "Key not valid for use in specified state." error on my scheduled SSIS package

And i think it isn't the same because if a execute my ETL from the Data Tools, it works just fine. It only throws error when it executes by the SQL Agent

Does anyone know what could be this? I haven't changed anyuthing in the Server, Database or SSIS Package.