That's odd Richard. The solver should be working anyway!!! I have a scenario that can cause the solver to fail, which is miss-aligned scope. If your scope is not properly polarly aligned, and you slew to a target, the solver may not be able to work as it only searches within a predefined distance from the target coordinates. It happened to me when I was totally off.
Mount is permanently on a pier; only the OTA and computer come in between sessions. The initial position appears to be fine, but I can check the PA next time out.
It doesn't appear that I mentioned before my error on the Gemini handset where the mount had been set for terrestrial tracking. I reset it to sidereal and closed and restarted EKOS between the reset and the log I posted. If the solver doesn't work next time, I'll take and save an image to solve on a load and slew to see what the apparent error is to help in troubleshooting.
Each time the solver stopped working for me it was because I changed kit, scope, FR or sensor and forgot to tell it. Worth checking that the FOV it thinks it has corresponds to your actual FOV. I maybe the only fool who has forgot to do this, but its worth checking.
Max
I faced the same issue and looks like my scope was off as well. I was able to fix it by increasing the search radius from 15 to 30. I wanted to share this so as anyone in the future may find this helpful tweak...