IIvadymII thank you for trying to connect the PC directly to the modem.
Double check Windows firewall settings are allowing BF6 public and private internet access.
On Windows, go to Settings → Privacy & Security → Windows Security → Firewall & network protection → Allow an app through firewall and confirm Battlefield 6 and your launcher are allowed on Private (and, if needed, Public) networks.
If still having issues then try changing IPv4 and IPv6 DNS server settings to Cloudflare DNS.
https://developers.cloudflare.com/1.1.1.1/setup/windows/
If both of these don't help and you still can't connect to BF6 even when the PC is plugged directly into the internet modem. Then it seems likely there's an ISP issue.
You can send your traceroutes to EA_Vendcera at the link below.
"Connection Failed" With Error Code 1:86001S:51002S:57019S | EA Forums - 12729012