Only works in Chrome/Edge it seems, but they don't tell you that until you've done the oauth and created a project, pretty shady.
Standard compliance, especially in something like a website builder should be a top priority. If the builder doesn't work in major browsers, why there be any confidence that the sites it produces will?
this is something we are going to solve soon by having ability to open up the build url and keeping it in sync with the changes.
It does not inspire confidence in an end product will work everywhere and be of high quality when the product to create it is buggy and limited.