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Connect Registration Failed

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Ultima actualización 5 months ago
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What happened? 

During the configuration of Prusa Connect on the Original Prusa MINI/+, MK4, MK3.9, MK3.5 or XL an error on this configuration can occur and the printer shows the message "Registration to Prusa Connect failed due to: ~". In place of ~, a text with more details is shown, from the list below. Depending on the specific shown text, there are different causes and fixes. 

Error name: Connect Registration Failed

Error code: #12401 (MINI), #13401 (MK4), #21401 (MK3.9), #23401 (MK3.5), #17401 (XL)

DNS error

The printer wasn't able to resolve the hostname of the Prusa Connect server into an IP address. The hostname is a unique label assigned to a device connected to a network. 

  • The printer is not connected to the network at all.
  • In case of a static configuration (non-DHCP), the DNS server is not configured or configured incorrectly.
  • The local DNS server is currently not working.
  • The Connect hostname is reconfigured to some that doesn't exist. For example, this can occur if loading a .ini file with an invalid configuration.


It's not possible to reach the server on the network level, hence it is not possible to establish a TCP connection. The system is either not answering at all or actively refuses the connection. 

  • The internet connection is not working, or a firewall blocks the communication.
  • In the case of a static configuration (non-DHCP), the gateway (typically, this is the IP address of the router) is not configured or configured incorrectly. 
  • The Connect server is under maintenance. 
  • Too many TCP connections are open with the printer, for example in PrusaLink. 

TLS error

This message points to an error doing a SSL/TLS handshake. This handshake is the process to create a safe and encrypted connection. 

  • Time is not synchronized on the printer (MINI/+). The time synchronization occurs for each internet connection, through the NTP server. It is possible this might take more time than initially expected, or rarely, that there might be issues with the server. 
  • A restrictive firewall (for example but not limited to a corporate proxy firewall) may restrict an automatic access to the NTP server. In that case, it will be necessary to manually allow the printer to access the NTP server.
  • Something in the path is trying to tamper with the communication, for example but not limited to an attack. 


The server claims that the printer is not authorized. The printer is not recognized as an Original Prusa. 

Server error

The server is returning a 500 Internal Server Error or similar. The issue is on the Connect side, and is expected to be fixed on its own. 

Internal error

This error is caused by an issue related to the printer firmware. 

Network error

Similar to the Refused error, but the connection dropped after it was initialized. 

  • Glitchy internet connection.
  • The latency to the Connect servers is too high. A geographic location is very far from our Connect servers can contribute to this cause.
  • The Connect server is temporarily down.

Protocol error

The response from the server is not recognized.

  • Bug on the server side. This cause is on our side and expected to be fixed on its own. 
  • Too old firmware on the printer and it's no longer supported.
  • A misconfiguration from the .ini file loaded on the printer, connecting to something different than our Connect server.

How to fix it? 

DNS error, Refused

Ensure that the printer is connected to the internet. In case of a static (non-DHCP) connection, ensure the correct settings are there, or test a DHCP connection. Also, check the .ini configuration file, and in case, rewrite the file. 

If the previous steps didn't fix the issue, attempt a factory reset

TLS error

Reattempt the Connect registration, after the printer is connected to the internet for a few more minutes. 

If the previous step didn't fix the issue, double-check your network firewall. Some firewalls will need for the NTP server to be allowed manually. The specific steps will depend on your specific firewall, we recommend checking your firewall documentation. 


If your printer is not an Original Prusa printer, it cannot use our Prusa Connect service.

In case your printer is an Original Prusa, re-flash or update its firmware

Server error

A server error indicates an issue from our side. The issue will be fixed on its own, try registering again to Prusa Connect later. 

Internal error

Re-flash or update the printer firmware. If this does not solve the issue, take note if the printer might have other issues, even if not directly related. 

Network error

Ensure that your internet connection is stable and not glitchy. To confirm whether an inconsistent internet connection caused the issue, test another connection, if available, such as a hotspot from your mobile phone. 

Protocol error

Ensure that the printer is running our latest firmware version. If it is running an old version, update the firmware. Also, check the .ini configuration file, and in case, rewrite the file.

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