Answer: The user.properties file location is %appdata%Sherlock i.e. usually in C:UsersAppdataRoamingSherlock Open this file user.properties in Notepad and find the line that starts with the word debugTags and delete that line. Then save the user.properties file. Sherlock 2020 R1 should start without issues. The entire text in Sherlock may include all the errors like example below: 12:48:32.970 INFO: Loading properties from user.properties 12:48:32.972 INFO: Converted debug tag ‘usePartsListUserPriority’ to advanced setting 12:48:32.975 java.lang.StringIndexOutOfBoundsException: String index out of range: -1 12:48:32.976 at java.lang.String.substring(String.java:1967) 12:48:32.982 at sherlock.config.User.convertProperties(User.java:142) 12:48:32.984 at sherlock.config.User.load(User.java:111) 12:48:32.986 at sherlock.ui.SherlockClient.SherlockApp.initConfig(SherlockApp.java:149) 12:48:32.988 at sherlock.ui.SherlockClient.SherlockApp.launchApp(SherlockApp.java:75) 12:48:32.990 at sherlock.ui.SherlockClient.SherlockClient.launchClient(SherlockClient.java:157) 12:48:32.993 at sherlock.ui.SherlockClient.SherlockClient.main(SherlockClient.java:125) 12:48:33.006 ERROR: String index out of range: -1