KB4577015 is still listed on Azure Update Manager but it cannot be installed cose it has been dissapeared on the MS Update Calalog list.

Please check for two things :

1. How old is the assessment data ? If you are not sure, please trigger one-time assessment to get the latest data.
2. Please check if your machine is getting the same data when you login to the machine and run check for updates. You may also want to check if your machine is connected to WSUS, then you may need to pull/approve the latest updates there.

@Wagrovidzki, Marek Thanks for reaching out. Kindly note that Update manager reports the patches which are listed from Windows Update in the machine. I would suggest you check if Periodic assessment is enabled on the machine. If enabled, trigger "one-time assessment" to get the latest assessment reflected and do let me know if the old KB is still reflected and do share a snapshot from Updates(Preview) tab ?