Diagnosis
The TDS (Total Dissolved Solids) sensor might be fouled with scale or needs recalibration. It's a common point of confusion because the sensor measures *all* ions, not just contaminants.
How to Fix It
First, flush the system. Put it in manual flush mode from the faucet panel and let it run for a good 15-20 minutes. This clears out any stagnant water and lets the new membrane stabilize. The reading should drop gradually.
If That Didn't Work
The sensor itself might need cleaning. You'd have to shut off the water, depressurize the system, and remove the sensor from its housing (usually on the manifold) to soak it in a mild citric acid solution to descale it.
Heads Up
If your incoming water is very hard or has a lot of chloramines, it can shorten the membrane's life and keep TDS higher than expected. A working system should typically get it under 20.