Update not verified macOS catalina

There is a problem with you current installation because the dialog states that it occurred while installing the selected updates. Be sure to copy the full installer application to a USB flash drive - 16GBs is the minimum size.

1. Is your computer eligible for the upgrade to Catalina?
2. Repair the disk using First Aid in Disk Utility.
3. Backup your files, and only your files.
4. Run the installer.
5. Prior to the installation you need to erase your disk. This can be done by the installer.
6. Try the installation once more.

Repair the Drive for El Capitan or Later

1. Restart the computer. Immediately, at or before the chime, hold down the Command and R keys until the Apple logo and progress bar appear. Wait until the Utility Menu appears.
2. Select Disk Utility and press the Continue button.
3. Then select the indented (usually, Macintosh HD) volume entry from the side list. 
4. Click on the First Aid button in the toolbar and wait for the Done button to activate. Click on it, then quit Disk Utility.
5. Select Restart from the Apple menu.

You can also make a bootable USB flash drive to install Catalina:

Bootable USB Installer for Catalina

First, review this introductory article: Create a bootable installer for macOS. Second, read this How To outline for creating a bootable macOS installer. Simply use the Terminal command by copying and pasting the command line below. You will need a 16GB USB flash drive that has been partitioned and formatted for use with OS X as well as an installer for the Catalina installer that you downloaded from the App Store.

Drive Partition and Format for the Flash Drive

1. Open Disk Utility in the Utilities' folder.
2. After Disk Utility loads select the flash drive (out-dented entry with the mfg.'s ID and size) from the side list.
3. Click on the Erase button in the Disk Utility toolbar. Name the drive, "MyVolume". <---- IMPORTANT!
4. In the drop down panel set the partition scheme to GUID. Set the Format type to Mac OS Extended (Journaled.)
5. Click on the Apply button and wait for the Done button to activate. When it does click on it.
6. Quit Disk Utility.

Create the Bootable Installer

Open the Terminal in the Utilities' folder. Copy the command line and paste that entire command line into the Terminal window at the prompt:

sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

Press RETURN. You will be asked for your admin password. It will not echo to the Terminal window. Then press RETURN again. Wait for the return of the Terminal prompt signifying the process has completed. It takes quite some time to finish. Be patient.

The bootable installer can be used to install Catalina. Shut the computer down. Insert your flash drive into a USB port. Start the computer like so:

Boot Using OPTION key

1. Restart the computer.
2. Immediately, at or before the chime, press and hold down the  "OPTION" key.
3. Release the key when the Boot Manager screen appears.
4. Select the disk icon for the USB flash drive.
5. Click on the arrow button under the disk icon.

I posted earlier the procedure for performing an Erase and Install using Network Recovery. If you follow those instructions, then you will be erasing the disk. Network Recovery involves connecting your computer to an Apple server via your Internet connection. The server will download and run the Utility Menu just like when you boot from the Recovery HD. You can choose to use this method instead of what I outlined above. In either case you will be erasing your disk, so be sure you have backed up your files before starting either procedure.

Krista_777 Said:

"I have been trying to update to catalina for months and i keep getting an error after it downloads that says the update cannot be verified. I have tried every solution I could find online & apple support including changing/ verifying the date & time etc."

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Scan your Mac for Malware:

Use MalwareBytes for Mac --- This is software that searches for malware/adware. So, scan with it and then remove what is found. Once removed, uninstall MalwareBytes for Mac. Then restart the Mac. Malware makes your Mac act in ways that are Malicious and unintended. So, give the scan a go.

Downloads:

1. Malwarebytes Anti-Malware for Mac
2. Malwarebytes uninstaller

Krista_777 Said:

"[...]I am downloading the full installer from the App Store It will fully download But then when it goes to begin the installation process I get the error"

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Reset your SMC and Your NVRAM.

• How to reset the System Management Controller (SMC) on your Mac - Apple Support
• Reset NVRAM or PRAM on your Mac - Apple Support

Changes occur, and sometimes, as a result, your Mac needs to reset itself. as a way to get back to its default operations. The ability to read from the USB port may have become manipulated technically. So, reset both, and see if it then works.

You are going about this all wrong if upgrading to Catalina is your objective. You need to download the full Catalina installer from the App Store. See How to upgrade to OS X El Capitan - Apple Support.

Do you now have a working system? If you don't, then follow these instructions.

Internet/Network Recovery of El Capitan or Later on a Clean Disk

1. Restart the computer. Immediately after the chime hold down the (Command-Option-R) keys until a globe appears.
2. The Utility Menu will appear in from 5-20 minutes. Be patient.
3. Select Disk Utility and click on the Continue button.
4. When Disk Utility loads select the target drive (will be the out-dented entry) from the side list.
5. Click on the Erase button in Disk Utility's toolbar. A panel will drop down.
6. Set the partition scheme to GUID.
7. Set the Format type to APFS (SSDs only) or Mac OS Extended (Journaled.)
8. Click on the Apply button, then click on the Done button when it activates.
9. Quit Disk Utility and return to the Utility Menu.
10. Select Install OS X and click on the Continue button.

These instructions will either install the last version of macOS you had installed on your computer or it will install Catalina.s

Repair the Drive for El Capitan or Later

1. Restart the computer. Immediately, at or before the chime, hold down the Command and R keys until the Apple logo and progress bar appear. Wait until the Utility Menu appears.
2. Select Disk Utility and press the Continue button.
3. Then select the indented (usually, Macintosh HD) volume entry from the side list. 
4. Click on the First Aid button in the toolbar and wait for the Done button to activate. Click on it, then quit Disk Utility.
5. Select Restart from the Apple menu.

Be sure you are downloading the full installer - How to upgrade to macOS Catalina. Use an Ethernet connection if you can because it's more reliable than Wi-Fi. If you use a slow connection, then you are more likely to get errors such as the one you've received.

Please read Writing an effective Apple Support Communities question. We are here to help. We are all users. We are not mind-readers nor clairvoyants. We only know what you write down and tell us. Be specific and thorough. Include your hardware information and installed version of macOS.

FYI: These are user-only forums. You are not speaking to Apple. if you need to speak with Apple Support, then contact product and tech support:  Contacting Apple for support and service including international calling numbers.

Thank you for your understanding and support.