Sometimes you may get the error like username is abcadm but defadm before GUI connect. This issue generally we get when using SUM DMO with system move option.
As a pre-requisite of DMO with system move. You have to re-install your target PAS host with the same SID as of source system and start the SUM again.
Reference SAP notes:
2510697 – Username is ‘abcadm’, but was ‘defadm’ before during GUI connect
3039196 – Error : Username is ‘abcadm’, but was ‘defadm’ before GUI connect. Scenario: SUM DMO with system move option