If you can access http://play.geforcenow.com in incognito mode then you will need to isolate which Chrome extension(s) are interfering with GeForce NOW. This can be done by going to chrome://extensions and disabling active extensions until the issue is resolved in normal browser mode.
If you still cannot access http://play.geforcenow.com, there can be Chrome extension(s) which could be active in incognito mode as well. Try disabling all the active extensions and see if the issue gets resolved:
- Go to chrome://extensions/
- For each active extension, click on "Details" and scroll down to "Allow in incognito" and disable if it is already enabled