macosmojave
I have the problem shown below when I try the update macOS:
I restarted the computer but I still have the same error. I tried to release the PRAM but it doesn't work. I don't know why I can't update. I try to update from macOS 10.14.6 to 10.14.6. I think maybe is a minor update because I also updated my MBP normally without any problem.
When you look at the Updates list in the Mac App Store, it will indicate in the info if a restart is required. Below is an example of this:
You will see the words Restart Required followed by an icon of a white triangle within a grey circle (looks like a reverse play button).
Prior to installing the update, just check the info against each update to see whether any of them require a restart.
Security updates and OS updates usually require a restart. Most other apps don't.
The first thing I would try is resetting the System Management Controller (SMC) of your Mac.
Since you don't specify the model of Mac it's not easy for me to set out the steps you need to take, so I refer you instead to this Apple Knowledge Base article: How to reset the System Management Controller (SMC) on your Mac.
Make sure you read through the article and follow the steps for your Mac carefully.
Best Answer
The latest 10.14.6 has sometimes its quirks to install. I suggest to uncheck "automatically keep my mac up to date".
Download the COMBO update and install it, https://support.apple.com/kb/DL2010?locale=en_US