First try this from a command window:
ipconfig /flushdns
If the problem persists, power down your router, wait 30 seconds, then power on.
What Gene Eric said. Flush your DNS.
What Spirochete said. Try other DNS servers.
Manually set those DNS servers in your computer system’s settings. List at least 4 DNS servers. You can look up DNS servers that are “free” online:
https://www.lifewire.com/free-and-public-dns-servers-2626062
My two cents- avoid: Google, Cloudflare, and Quad9 “free” DNS servers.
Check your hosts file. You might enter a line:
45.79.56.181 freerepublic.com
or
45.79.56.181 www.freerepublic.com
If your Internet browser is set up to block cookies in general, or 3rd party cookies, you will need to manually set your Internet browser to accept cookies for domain name:
freerepublic.com