With xfce4-sensors-plugin 1.3.90 compiled from source under arch linux, sensors values are not shown after session logins if "don't show tooltips" got activated during a previous session: sensors labels are shown correctly, but their values are missing until opening "plugin properties"; then values get shown, but they disappear again on next session, unless I deactivate "don't show tooltips". It's always reproduceable.
Fabian referenced this bugreport in commit 7b3f0a9488543f5a8a8c332e1b0d0803dd68e689 Fix bug 15038 with not updating sensor values without tooltips set https://git.xfce.org/panel-plugins/xfce4-sensors-plugin/commit?id=7b3f0a9488543f5a8a8c332e1b0d0803dd68e689