I have run the update feature 3 times and it is still diplaying 1 missing update although it says 3 times succesfully installed
Can you give some more details? Windows or Linux? What KB is the update? Has the update actually installed on the machine or is it failing to install?
Joe H. commented
Here it happens all the time with KB2267602 (Defender Update). Even if you installed the most recent one, older ones appear to be listed as missing.