I am having a similar issue in title.
The result however sounds slightly different in that I get a new tab after clicking next. I can complete the login process but the tab is stuck. Interestingly the page title says "Keeper SSO login success" so it appears as if something isn't being passed on the the extension.
The extension is from popular extensions.
Also seems worth mentioning that I had a problem logging into the Keeper desktop app to. I don't know if it's relevant to the extension problem. I had to disable the preview window otherwise it had the same "stuck" behaviour.
Version 0.99.131.0.1-beta