Hi Salman,
Can you please share a screenshot of your Request For Change screen with the error.
Also there are at times other dependencies regarding approver and creator. You might want to check that. I mean the approver should be setting the document to in development.
You can also check the logs for your id in tcode SLG1 in solman system.
Finally it would be wise to use st01 and check for sure that it is not authorization issue.
Hope it helps.
Best Regards
Robin Singh