make sure it is the right resin mb40 or equivalent , some resins are designed to work within a specific range and you will never get them down to zero, also make sure your handheld tds meter is functioning correctly.
Some times they need calibrating, I would buy a second meter from a different scource so you can check them against each other.
If you are only getting a reading of 2 through a 30l vessil, I reckon it has to be 100% your tds meter,