Problem-solving with the Rodx probe displaying 9.9: Technical Advisor's Guide

Client:
Hello, I have a problem with my rodx probe which displays 9.9

Technical Advisor:
Hello, one moment

Client:
What should I do????

Technical Advisor:
https://ph-redox-pool.com/gb/content/17-ma-sonde-redox-est-elle-hors-service-