You can try sudo apt update then reboot. See if you have errors showing about an unreachable repository.
See if it fails again. It could be and issue with your dns server. There is a logfile firstboot.log I believe. It may give more details on the failure.
I had an error today on the openhab repository, not sure why but it worked a couple tries later. Maybe you experienced the same issue. If it does not work after a reboot, I would try re-make the sd card. If that does not work post your results with the first boot log and the team here should be able to offer suggestions.
Here we are…
My 1st question here is, what is the difference between the newest raspberry pi OS and the one suggested by OpenHAB since they appear to be base on buster but I have a filling this is not entirely accurate.
Hello, I am using the Rasberrypi 3 B plus model with [v1.6-alpha] on my 16gb microSD. I am also facing the same problem as you did. I did forma my SD card and tried severarl times, but it doesnt work. The website is still not reachable. Please help me out