Cal Aqua Labs Indicator solution 60 ml

I bougth the two Cal Aqua (reference and indicator) and the Cal Aqua Double Checker.

The indicator solution works for the first measure and kept always in the same value. My Co2 injection works between 12 Pm and 20 PM. In the middle of this period the reagent doens´t change colour and it should as CO2 evaporates from the tank.

I try again by removing the reagent and put another dose in the drop checker and still the same issue. Since it turns green

never comeback to blue. (?)

Can´t figure why.

Best regards