Windows says I need an update but there is no update available

In the bottom right of my desktop I have an update symbol with a red dot, when I click it opens the update page in settings. It says "You're up to date" but it also says "Your device is missing important security updates. Make sure to keep your device on and plugged in so updates can complete." I have had this on my computer for at least 8 months now and I'm not sure what to do or whether it is really an issue or not.