Hello Henrylb,
I recommend unplug the power to the two min boxes and reconnect the ends of the coax to the wall and the mini boxes. Once the power is reconnected and the boxes load, please go into the receiver settings and turn Sap off, then back on. Steps to turn SAP off/on are found on our website. https://www.cox.com/residential/support/turning-sap-on-or-off-on-the-mini-box--dta.html
If this doesn't work, then the Mini boxes may need to be replaced at a Cox Solution Store. https://www.cox.com/residential/contactus.html is a link to our website with a map of store locations. You may need to enter your local information on the top right to get a local map.