AEG AX91-404 Error Code Filter not recognized: Meaning, Fixes & Troubleshooting

AEG AX91-404 error code Filter not recognized means the AEG Wellbeing app or the purifier's firmware cannot identify the installed filter. This can happen if the filter is not the correct model for the AX91-404, was not installed correctly, has missing or damaged identification (such as an RFID or tag used by the device), or if the purifier's sensor/firmware cannot read the filter. The message 'AEG AX91-404 error code Filter not recognized' is intended to prevent operation with an unverified or improperly installed filter.

• The app shows 'Filter not recognized' or similar status instead of filter life.
• Filter replacement prompt repeats after reinstalling the same filter.
• The purifier may run in limited mode or refuse certain features until a recognized filter is installed.

• Incorrect filter model or non‑OEM aftermarket filter that lacks the purifier's identification.
• Filter not seated correctly or protective packaging/material left in place.
• Temporary communication glitch between purifier and app or firmware requiring a restart.

1. 1
   Confirm filter compatibility
2. 2
   Inspect filter and housing
3. 3
   Update firmware and app
4. 4
   Reset pairing and re-add the device
5. 5
   Try a different filter to isolate the issue

• Installing the filter without removing protective packaging or plastic wrap.
• Assuming any similar-sized filter will be recognized — the purifier expects specific identification.
• Skipping app/device restart after replacing the filter; transient states can persist until a restart.

• Do not force-fit a filter or push connectors by excessive force — do not damage clips or housing.
• Do not attempt to modify or tamper with the filter's identification tags, chips, or labels to make it appear recognized.

• Always unplug the purifier before removing or installing the filter to avoid electrical risk.
• Do not wash or wet disposable filters; replacing them with an appropriate new filter is safer than attempting repairs.

If you have tried the steps above (reseating the filter, power cycling, updating the app/firmware, and trying a confirmed-compatible filter) and AX91-404 error code Filter not recognized persists, contact AEG support. Provide the purifier serial number, the filter part number, and the troubleshooting steps already attempted. See the AEG support article for related guidance: https://support.aeg.co.uk/support-articles/article/the-app-displays-filter-not-recognized-error-message.

• Use only AEG‑listed compatible filters for the AX91-404 (check part numbers on AEG accessories pages).
• When replacing filters, remove packaging completely and confirm the filter is seated correctly.
• Keep the purifier's filter compartment clean and perform regular app/firmware updates when available.