Poor DEF quality no check engine light

[FnG92]

2014 t800 isx15 2350. Dash lit up with message piir def quality and gave me a 2 hour timer for derate. I pulled over and topped off my def tank with less than a full spare def box I carry on the truck. My def gage is full with a red light lit up. Any helpful suggestions on what to do would be very appreciated!