Are you using two-factor authentication with Arlo? If so, we don't support that yet. You can work around this for now by sharing your camera with another account that's used only for Camect access without two-factor turned on.
If you're not using two-factor, then shortly after trying to sign in and getting a failure, please use "Report Bug" from the home settings (cog wheel at top right) to send a bug report, and check the checkbox to include logs and settings from your device.