Jumia — voucher with code ap4513141

I got this voucher some weeks ago after a used headphone was delivered to me and i complained. I have been having payment issues while trying to use the voucher and ive left it for some weeks as i was told it would reset after 24 hrs but its still saying invalid voucher code and i was tols it is valid for 90 days
Please i need this to be looked into critically. Thanks