CrIVO2 + KNVO3 + 2 KOH KNIIIO2 + K2CrVIO4 + H2O

This is an oxidation-reduction (redox) reaction:

NV + 2 e- NIII (reduction)

CrIV - 2 e- CrVI (oxidation)

KNO3 is an oxidizing agent, CrO2 is a reducing agent.