Hello Mouaz,
Thanks for reading through and trying to help me out. Although a license is manually assigned, the order remains on block. When assigning the license, error message "License is required for country US SG IN (see log)" occurred so I thought maybe that is the problem. so I assigned partner group PGLDT2 in config and the error message disappeared. However, after license assignment, the sales order is still blocked. That is the real problem.
Here is the screenshot after the license assignment. (Note that this problem happens only when license type is not NLR):
It shows in the blocked document report and also has red traffic light.
Thanks,
Satish