Fix #3: Check Roblox server status. Sometimes, a Roblox game may not launch or return an error like the HTTP 503 service unavailable when you try to open it because of an on-going server trouble.

While the traditional way to play Roblox is through the dedicated desktop application, players now have the option to enjoy Roblox games directly in their web browsers using a service called Now.gg.

Also, allow the Roblox Player and the ports required by Roblox through the firewall. Disable your VPN to boost your internet speed and flush the DNS cache to fix network connectivity issues.