WireShark install fails on Windows 10 with error 1603
The error points to not not having the VC++ redistributable installed. However, this is Windows 10 build 17763.615. There is no upgrade available for the VC++R. I only see VC++ 2008,2010,2013 & 2015 in my installed updates.
Build 17763.615 appears to be a not quite up to date variant of 1809, MS lists the current 1809 build as 17763.652 here.
As you say there should be no issue with the VC runtime on that OS.
Which version of Wireshark and is it a regular release, or built by yourself?
Win 10 - 1809, you are correct. WS 3.03 x64 downloaded from the site, no changes made.
Are you using the .exe installer or the .msi version?
exe installer.
The release builds run the VS2017 version of the vc_redist.xxx.exe, using the following command line:
where xxx is x64 for a 64 bit Wireshark build and x86 for a 32 bit build.
Can you grab the appropriate version from here and run it with a simple command line of
...exe /install
from an elevated prompt. I'm hoping that doing that will let the installer will reveal the issue.