This issue is presenting in different ways across Windows and Mac devices.
Windows:
When install fails while the FV-Launcher is updating, first try to Uninstall the Launcher by going to Settings, then Apps, find the Futureverse Launcher, click on the menu icon and select Uninstall
If the install continues to fail, use the following file path to find the AppData folder C:\User\{UserAccount}\AppData\Local\Programs\f-v_-launcher
Where it has {UserAccount}, for you this will be an abbreviation of your Windows Login
Find and run the Uninstall Futureverse Launcher application which should remove any Launcher related files more completely and resolve this issue when reinstalling.
Mac:
If the install is failing, first ensure that you have downloaded the correct version for your device type (Apple Silicon (M1, M2, M3) or Intel Processor) - you can verify which you have by clicking the Apple icon in the top left and selecting About this Mac
Next, remove the Launcher by opening Finder, search for Futureverse, then drag the Futureverse Launcher into the Bin found in the dock, and then empty the Bin and restart the machine. Then download and attempt to install the Launcher again
If you get a JavaScript error when trying to install the Launcher, open Terminal (open Launchpad and type in "Terminal", then click to open Terminal) and paste the following command into the terminal and hit Return
softwareupdate --install-rosetta
Once a message is received saying Rosetta install has finished, restart the machine and then try the install again.