If you Log in to the system in the language in which the units are lacking or keep the using transaction CUNI. You should deactivate the conversion exit during T006 table you can open transaction SE16 (Settings > User parameter > Tab Data Browser > Consider conversion exit cannot be selected).If you cannot find the value in the T006 or TCURC, you should insert value.
If you have the error massage and received this error message for the initial value, this means that there is an inconsistency in the SID table for the 0UNIT or 0CURRENCY characteristic. You should eliminate this repugnance by calling the RSDMD_INITIAL_LINE_INSERT function module with I_CHABASNM = 0UNIT or 0CURRENCY.For Unit - table T006 and for Currency - table TCURC should have data Please check whether ZUNIT info object is correctly defined. Compare it with info object 0UNIT.
You can also try SID Conversion checks and changes, the path is Tests in Transaction RSRV => All Elementary Tests => Master Data => SID Conversion for Information Object 0UNIT.If units are loaded in the format of external, if you get and change the internal format in the transfer or update rules or change files. You cannot CONVERSION_EXIT_CUNIT_INPUT function module converts the external value of a unit into the internal value we are giving some solution of SID found value on PC of zunit.