I have discovered a bug in the designer launcher / gateway settings.
I started a project on a docker container that used port 80, 443 for the ports with "force redirect to secure port" on.
I took a backup of the gateway from the docker container, created a windows VM, installed ignition and then restored the gateway backup.
Ignition loaded perfectly in the browser, but when I tried to launch the designer launcher, apparently the designer remembered that the server used to redirect to port 443 and failed to download dependencies and wouldn't load.
However, when I went onto the gateway, set it back to port 80/443 with secure redirect, all of a sudden, the designer was able to download the dependencies and open the project.
This means there must be a bug where when the gateway restore happens, the port the designer thinks it needs to connect to is wrong and there is no indication to the user that this is the problem.