• Make sure your operating system is updated
• Automatically sync your system time
• Disable all add-ons, extensions and VPN
• Clear browser cache
• Try a new browser/client
• Restart your computer and your router 
• Close all other applications
• Ensure you're not being blocked from parental or network controls
• Check firewall or third party firewall software (or any internet software in general)
• Temporarily disable anti-virus and test