Can a VPN or proxy cause 'Roblox error code 403 an error was encountered during authentication'?

Yes, absolutely. VPNs and proxies can sometimes interfere with Roblox's authentication process. They might route your connection through servers that Roblox flags as suspicious, or they could cause latency and connection instability that disrupts the secure handshake required for authentication. If you're using a VPN or proxy and encounter this error, a crucial troubleshooting step is to temporarily disable it and attempt to log in directly. If it resolves the issue, you might need to try a different VPN server or service.