windows security centre keeps telling me my antivirus is out of date, help!

i have mcafee antivirus, an icon appeared to tell me that my antivirus is out of date, but my antivirus is still working normally, but the windows security centre keeps telling me that is out of date. i have also updated the antivirus twice, but it keeps telling me that it is out of date. what appears to be the problem exactly, any help pls? thanks