Use an incognito/private browser window: http://192.168.1.9:32400/web
You were attempting to connect via Synology QuickConnect (maybe clicking on “open” in the Package Manager). That is not supported for the initial setup. You have to connect direct to the NAS using it’s IP address.
Also, logs show you are running 1.25.3.5409. Stay there. Do not go back to the version in the Synology Package Manager, 1.21.0.3744. There have been several changes since it was released. Falling back will cause difficulties.
Some documentation to peruse:
