Diagnosis
You've got fresh filters but the system's smart chip didn't get the reset memo. Yeah, this one's common. The TDS sensor and the filter life timer are on separate circuits.
How to Fix It
You need to manually reset the life counter. Press and hold the 'Select' and 'Flush' buttons on the faucet's control panel at the same time for about 5 seconds. You'll see the screen flash and then show the reset symbol. That should clear the 'expired' message and start the countdown from 100%.
If That Didn't Work
The filter cartridges might not be seated all the way, or the RFID chip on the new filter isn't making contact. Turn the system off at the main valve, pop the filter housings open, and reseat the cartridges firmly. Make sure you hear a click.
Heads Up
If you use third-party filters that don't have the Waterdrop RFID chip, the system will always show 'life expired.' It's a proprietary thing.