In this regard, I have already created a Request (Request #34214465) twice but got no response.
when can I get a reply?
You need to send an email to freelancersuccess (at) upwork (dot) com, with the contract number and whether you want to remove only the impact of the contract on your JSS or if you want to also replace the public feedback with "This feedback has been removed"
This is assuming that you haven't used the perk in the last 3 months and the last 10 contracts.
I reached out to the team handling your case and one of our agents will follow up with you on your support ticket as soon as possible to assist you further.
Thank you for your patience,