You have upgraded the SAP system from Non-unicode to Unicode. As part of upgrade task, you need to change the affected connections in transaction code SM59 to Unicode.
So, execute transaction code SM59. Jump to MDMP & Unicode tab and switch to change mode. Select the Unicode button, click Save and do the connection test.
[Note] If you click on the change mode but cannot do the modifications – It means that your SAP system is Non-Unicode.
