iMac Update

My iMac has automatic updates but the most recent update that it needs which it says it is the macOS 10.14.6 update, won't download. When I go to system preferences and click on software update, it says checking for update, and then the update appears and I click update now, and it starts to update and it has been updated about halfway but hasn't completed the last half of the update. So after it updates for a couple seconds a screen pops up saying something about please make sure you're connected to the internet but I am, my internet is working when I try to search something or use anything else on my computer, so I'm just not sure why it won't update. Thank you!!!!