I am encountering this problem when installing home assistant using Raspberry Pi 5.
I tried to re- install home assistant on the SD card but same error.
Is your provider or router maybe preventing access to NTP servers? We use Cloudflare NTP.
Another probelm could be DNS. Make sure the DNS server your DHCP provides is valid and working. If your DHCP (router) does not provide a DNS server, the system does fallback to Cloudflare. It could also be that your router/firewall filters Cloudflare DNS service.