---
title: "Link’nX KNX functions: troubleshooting and frequently asked questions"
description: "Link’nX function with no effect, hysteresis not repeated, timer that never ends or save rejected: the causes and the checks to run for KNX functions."
canonical: https://wiki.can-nx.com/en/guides/link-function-help/
language: en
product: Link’nX
audience:
  - administrateur
  - installateur
context: "Link’nX web: hysteresis and presence detection functions"
---

# Link’nX KNX functions: troubleshooting and frequently asked questions

Context: Link’nX web: hysteresis and presence detection functions

Equipment that does not react, hysteresis output not repeated, timer that does not end, save rejected or function missing: here are the answers to the most common problems with Link’nX functions, for administrators and installers. Always start by checking the project and the gateway displayed.

## Do I need to add my function to a scenario?

No. A configured and enabled function directly commands its KNX target according to its settings. To find it and check its state, follow the [functions guide](https://wiki.can-nx.com/en/guides/link-function-edit/).

## Why does my equipment not react when the demo works?

**Play demo** and moving the marker in the [hysteresis preview](https://wiki.can-nx.com/en/guides/link-function-hysteresis/) are simulations: they send no KNX command. Then check:

- that the function was saved and that its card shows **Enabled**;
- that the source, the target and their DPTs match the known parameters of the installation.

Do not change a value to try to cause a reaction whose effect you do not know. If the result is still missing after these checks, contact support.

## Why is the hysteresis output not sent again at each measurement?

This is the expected behavior for a numeric source: the command is requested when entering a threshold zone. Successive measurements within the same zone do not repeat it, and the deadband requests no sending. The [threshold rules](https://wiki.can-nx.com/en/guides/link-function-hysteresis/) detail this behavior. For a binary source or another situation not covered, contact support with the result you want.

## Why does the timer not end although the room appears empty?

The function monitors telegrams, not room occupancy: a new write or response on any of the sources restarts the delay, even with the value zero. Check the addresses in **Sources** and their known use. If the chosen sources do match the objective, follow the [timer guide](https://wiki.can-nx.com/en/guides/link-function-presence/), then report the symptom to support if the result remains unexpected.

## Why doesn’t the preview show the same number as the delay field?

The units differ: the entry field is in minutes, the preview rule in milliseconds and the list card again in minutes. For example, 2 minutes correspond to 120,000 ms. If the conversion does not match your entry, contact support without repeating saves.

## Why is saving the function rejected?

With **Please fill in all required fields**, check **Function name**, 80 characters maximum, then the settings of the type displayed:

- hysteresis: the addresses, the DPTs, the two output values and a low threshold strictly lower than the high threshold;
- presence detection: each source, the target, the DPT, the value and a positive duration.

The guide for each type explains the expected formats. If **Error saving** or **Error updating** persists, send the message to support.

## Where can I find a function or all its sources?

Check the project and the gateway, then the two groups of the **Function list**. **No function in this group yet.** concerns one group; **No function configured yet.** concerns the whole list. To see all the sources of a presence function, open its **Edit** pencil. If the list remains unexpected, contact support before recreating a function.

## Does disabling or deleting a function restore the previous state of the equipment?

No: these operations send no reverse command. To suspend a function while keeping its configuration, use **Enable or disable function**, wait for the confirmation and check its state. To restore a physical state whose procedure is not established in your context, contact support.

## Contact support

If the problem persists after these checks, write to support@can-nx.com with: Link’nX — Functions, the project and the gateway, the name and type of the function, the state displayed, the symptom, any message and the tests already made. A screenshot without sensitive data can help. Never send a password or a secret.