After about 50 attempts this morning to start WeatherCat, after giving up last night and just turning the PC off, I did a restore to Sierra this morning. When WeatherCat restarted, it downloaded all the data with no problem and has been running fine since. It is obvious to me that I have some incompatibility issues with Davis, High Sierra, Silicon Labs and WeatherCat. High Sierra gives me nothing I need, other than always wanting to be on the latest and greatest, so I'll just stay where I am for now. If I run clean for a week or so, I'll upgrade WC to 2.4.3, the rollback put me back on 2.4.2.