The "Connection failed…" message is displayed when you are using DSM or Synology desktop utilities.

Error occurred in DSM

1. Connect a computer to the same local network as your Synology NAS and disable the Wi-Fi on the computer. If the computer cannot connect to the Internet, please check your network environment (e.g., gateway, DNS server, and proxy server settings) first.
2. At DSM Control Panel > Network > General > Manually configure DNS server, set the DNS server value to "8.8.8.8" or "1.1.1.1". If you are located in China, use 114.114.114.114 or 223.5.5.5 instead.
3. At DSM Control Panel > Network > General > Proxy, disable Connect via a proxy server. If disabling this feature can solve the problem, please check the proxy server settings in your network environment and ensure that your proxy server allows access to the websites listed in this article.
4. At DSM Control Panel > Network > Network Interface, select a network interface and click Edit > IPv6. Make sure the IPv6 setup setting is Off. Also, please select DHCP and disable the MTU setting in the IPv4 tab.¹
5. At DSM Control Panel > Security > Firewall, temporarily disable Firewall. If you wish to enable the firewall again, make sure to add the IP addresses listed in this article to the firewall rules to allow access to specific websites through ports 80 and 443.
6. At DSM Control Panel > Security > Firewall > Firewall Profile, make sure the websites that Synology NAS connects to when running services or performing software/package updates are not set to Deny. Please refer to this article for more information.
7. At DSM Control Panel > Regional Options > Time > Synchronize with NTP server, click Update Now to sync the system time with the NTP server.

Error occurred in Synology Desktop utilities

1. At Package Center, check if the package you are using is in Running status. For example, if you are using Surveillance Station Client, check if Surveillance Station is in Running status.
2. At DSM Control Panel > Network > General > Manually configure DNS server, set the DNS server value to "8.8.8.8" or "1.1.1.1". If you are located in China, use 114.114.114.114 or 223.5.5.5 instead.
3. At DSM Control Panel > Network > General > Proxy, disable Connect via a proxy server. If disabling this feature can solve the problem, please check the proxy server settings in your network environment and ensure that your proxy server allows access to the websites listed in this article.
4. At DSM Control Panel > Network > Network Interface, select a network interface and click Edit > IPv6. Make sure the IPv6 setup setting is Off. Also, please select DHCP and disable the MTU setting in the IPv4 tab.²
5. At DSM Control Panel > Security > Firewall, temporarily disable Firewall. If you wish to enable the firewall again, make sure to add the IP addresses listed in this article to the firewall rules to allow access to specific websites through ports 80 and 443.
6. At DSM Control Panel > Regional Options > Time > Synchronize with NTP server, click Update Now to sync the system time with the NTP server.
7. Connect a computer to the same local network as your Synology NAS and disable the Wi-Fi on the computer. Open the Synology desktop utility you are using. If the error occurred only when the computer is located on a different network, please check your network environment (e.g., gateway, DNS, proxy server, and port forwarding settings).