If you get the error MSI returned failure code 1603: Fatal error during installation when installing your Redgate tools, it could be a requirements issue so you may want to check that you meet the requirements for the tool you're using on the documentation site first.
After the failed installation attempt, try browsing to C:\Users\[USERNAME]\AppData\Local\Temp\Red Gate\CFU and find the installer, then right click "run as administrator".
If the problem persists, run the following from an elevated command prompt:
>netsh http show iplisten
If there are no rules, then by default all services are on the AllowList. However, if the default is changed or if there is at least one rule then it may be necessary to add an extra one.
What you may see is "::" as a rule after running the above command. This is a rule that likely would have been added by another app. (changes to these rules are not monitored so it isn't possible to tell which app added it). If that is the case though then you will need to apply the rule below.
>netsh http add iplisten 127.0.0.1
Once added please try to run the installer again.
The rule can be removed if needed by using the following command:
>netsh http delete iplisten 127.0.0.1
If you are seeing a slightly different error message such as:
"MSI returned failure code 1603: fatal error during installation.
The installer has encountered an unexpected error installing this package. This may indicate a problem with this package. the Error code is 2343."
Then this could indicate an issue with either the installer or there could be another app blocking the installer. To test this please try installing the tools on a non-work machine. If the install is succesful this indicates that your work machine has a security policy blocking the installer. Please check with your IT team to see if any Antivirus or a third party tool (for example one that moderates access/privileges management) is blocking the installer.
If this doesn't help please raise a support ticket.