Hi Eswar,
What I understand from your post is you are trying to get GTS block status for a Sales Order in change/display mode. This is not the way GTS is designed. GTS block status is not stored in ECC. ECC makes a call to GTS everytime to get the latest status.
You can use transaction /n/SAPSLL/BL_DOC_SD_R3 (Export documents) or /n/SAPSLL/BL_DOC_MM_R3 (Import documents) to display blocked documents in ECC. Please note, documents not blocked will not be shown here.
Alternatively, you can always login to GTS to make use of various standard reports to display document status.
Hope this helps.
regards,
Kul Vaibhav