This warning message just started happening yesterday. We have not updated any of our desktop version except for one machine that has arcmap desktop 10.6. But all of our arcmap desktops are experiencing this issue. Once we click ok through it the find tool will work. But once you close your session and go back into arcmap and try the find tool again it does this warning all over again. Did something change on ESRI's end that cascaded down somehow to our desktops even though we are not connected to ArcGIS online?