Unban problem

Hi, I'm sorry if my language is bad because english isn't my first language. I want to report a problem that I am experiencing right now. I can't unban one of the player in my server. When I /pardon (the player), it said that nothing change, the player isn't banned. But when I check the banlist the player is there. I hope you can give me a feedback on how to solve this problem. Thank you for your time.

Thank you for your your reply. The thing is that I did that already. When I press the trash can button, the player's name is gone from the banlist but the player said that he is still ban and when I refresh the banlist page the player's name pop up again. I try it many times and the same thing happened. Anyway, I really appreciate the fact that you take your time on trying to help. Thank you

No I did not install any plugin and actually I forgot to mention something. I've tried to unban other player and it work just fine but only this one player I can't do anything about.

Well I guess that is a solution. Thank you both Alex[ES] and MiataBoy for helping me solve my problem.