What confirmation do you have that the user ID you are using has the requirement checked out?
Is this a brand new requirement, or are you trying to change an existing requirement?
Information regarding who has a given entity checked out is stored in Shadow tables in the project database. These are tables named VC_* that mimic the related table (i.e. REQ for requirements) and also include additional fields to track who has the item checked out. The info in these tables can be accessed by your DBA, or through Site Admin. Have one of those people look at the VC_REQ table to confirm that there is an entry there for the Requirement you are working with, and that it records your user as the one who has it checked out.
If you user is not the one who has it checked out, then the user who does have it checked out needs to check it in first or undo their check out. Then you can check it out and make you modifications and check it in.
If there is no entry in the VC table for your requirement, then you need to first check it out and then make your changes.
Is this a brand new requirement, or are you trying to change an existing requirement?
Information regarding who has a given entity checked out is stored in Shadow tables in the project database. These are tables named VC_* that mimic the related table (i.e. REQ for requirements) and also include additional fields to track who has the item checked out. The info in these tables can be accessed by your DBA, or through Site Admin. Have one of those people look at the VC_REQ table to confirm that there is an entry there for the Requirement you are working with, and that it records your user as the one who has it checked out.
If you user is not the one who has it checked out, then the user who does have it checked out needs to check it in first or undo their check out. Then you can check it out and make you modifications and check it in.
If there is no entry in the VC table for your requirement, then you need to first check it out and then make your changes.