Can't install the update 10.13.6 Error 602

You might try this.

I found it here

https://support.apple.com/en-ae/HT209170

If error 602 occurs when installing an Apple software update

Error 602 can occur when the installer can't make the Internet connections it needs to complete installation. Check your network settings or configuration.

When installing an Apple software update, you might see an alert saying that an error occurred installing the update (602). Try these solutions:

• To find out whether the alert is related to the network settings on your Mac, you can use Network preferences to add a network location. If the default settings in the new network location don't help, you can easily switch back to your current network settings.
• If you're using third-party firewall software or other security software, it could be blocking the network access required by the software update. In that case, either reconfigure the software or temporarily disable it until after installing the update. 
• If your network is using an authenticated proxy (common in some enterprise environments), you might need to check with your network administrator or install the update from a different network. Some authenticated proxies don't allow the specific Internet access required by Apple software updates.

Is this the update you are trying to install, Download macOS High Sierra 10.13.6 Supplemental Update for MacBook Pro (2018)

It might be that you need to update your Mac from 10.13.5 to 10.13.6 before you can install the Supplemental update for your Mac. Download macOS High Sierra 10.13.6 Update

Oddly enough, I clicked on this link Download macOS High Sierra 10.13.6 Supplemental Update 2 for MacBook Pro (2018)

and downloaded the pkg file onto my desktop (same MBP that wouldn't allow for the update through the App store) and then when it finished downloading, I simply clicked on the file and voila, it updated the OS.

Another user reported this error (which makes no real sense in this case) and found that the issue was his company Proxy was not allowing his Mac to contact Apple to confirm the ability to install this package.

They took the computer to Starbucks to complete the Install.

I did have this problem too, and I've solve it now.

I found this happened because some setting of my Shadowsocks client not allowing my Mac to contact Apple to confirm the ability to install this package. Then I just closed the Shadowsocks client and the update successed.

Hope this would help.

I was able to turn off my proxies in the network settings and the download went through no problem. 13" MBP 2018.

See to following to turn off your proxies (uncheck all the listed proxies):

https://www.linksys.com/us/support-article?articleNum=135932

Once you have followed the above instructions, re-try the download and everything should go through.

The easiest way I have found to solve this issue is to change the location in the wifi setting. Instead of the standard one, I created a new one (with another name) and connected to the wifi from that new "location". Everything went flawlessly.

The issue you are experiencing could have to do with some sort of proxy that you have installed on your Mac as one of the other comments in response to your thread indicates. In that respondents case, his company was routing all his traffic through a proxy, and thus when s/he left the office and went to a Starbucks, where the proxy wasn't present, s/he was able to install the patch. My case was a little different, but also related to proxying software.

I have a corporate issue MacBook Pro 15" running High Sierra 10.13.6. Whenever attempting to use the Mac Store app to apply the 10.13.6 supplemental updates (including iTunes 12.8, Safari 12.0.1, and Security Update 2018-002 10.13.6) it would fail during the installation phase with "An error has occurred. An error occurred installing the update. (602)". It has been very difficult to find any concrete answers to this question online, and I ultimately used the Console app on the Mac to provide me with some clues as to what might be happening. This row from my Console log shows the failure, and the primary clue for me was that NetworkRequired = true.

Operations failed with error: Error Domain=BOSErrorDomain Code=204 "An error occurred during preflight." UserInfo={NSLocalizedDescription=An error occurred during preflight., NSUnderlyingError=0x7fb369224b50 {Error Domain=BridgeOSSoftwareUpdateError Code=19 "MSU - 2 (Failed to personalize with options.);MSU - 2 (Could not personalize boot/firmware bundle.);AMAI - 3099 (AMAuthInstallBundlePersonalize() failed: );" UserInfo={NSLocalizedDescription=MSU - 2 (Failed to personalize with options.);MSU - 2 (Could not personalize boot/firmware bundle.);AMAI - 3099 (AMAuthInstallBundlePersonalize() failed: );, MSUErrorCode=2, AMAuthInstallErrorCode=3099, MSUErrorDescription=Failed to personalize with options., NetworkRequired=true}}}

Additionally, I saw a number of other rows above this one in my console log from a bosUpdateProxy process that was brokering TLS handling (managing data encryption). The big "ah hah" for me was that I had proxy interference, further substantiated by the Starbucks respondent, so I started digging around on my Mac for proxying software, and came upon a new app/service that my company uses called Zscaler.

I was thankfully and with great relief able to solve the issue by setting the Connectivity Status of the installed Zscaler application on my Mac from "On" to "Off" (I did not uninstall it -- just turned it off) and then trying the install through the Mac Store App again. Once it was "Off" I was able to install the supplemental update software successfully to my Mac.

I hope this helps you or someone else suffering from the same problem.

FYI, I was able to resolve the issue with my initial inclination to remove the download cache. 

sudo rm -rf /Library/Updates

Seems like the download was interrupted somewhere, hence the 602 error. So instead of doing an HTTP/FTP resume it kept giving that error.

I have no idea.

Maybe others will know.

602 is a network error. Uncheck “Auto Proxy Discovery” in System Preferences > Network > Proxies. (thanks Steven and Mariah).

for this not familiar with that feature, it is described here:

How to use network locations on your Mac - Apple Support

.

"Starbucks" is not the solution, per se.

"Out from under the restrictions of you corporate Network Proxy" is the actual solution.