Taskcoach mentioned errors which I found in the error log and taskcoachlog.
In the taskcoachlog:
/usr/lib/python2.7/dist-packages/taskcoachlib/notify/notifier_libnotify.py:31: PyGIWarning: Notify was imported without specifying a version first. Use gi.require_version('Notify', '0.7') before import to ensure that the right version gets loaded.
import gi.repository.Notify
xUbuntu 18.10 xfce. Errors in the .xsession-errors log:
(taskcoach:32627): Gtk-CRITICAL **: 10:40:06.321: gtk_widget_set_size_request: assertion 'height >= -1' failed
10:40:06: Debug: ClientToScreen cannot work when toplevel window is not shown
10:40:06: Debug: ScreenToClient cannot work when toplevel window is not shown
(taskcoach:32627): Gtk-CRITICAL **: 10:40:06.365: gtk_widget_set_size_request: assertion 'height >= -1' failed
10:40:06: Debug: ClientToScreen cannot work when toplevel window is not shown
10:40:06: Debug: ScreenToClient cannot work when toplevel window is not shown
10:40:06: Debug: ScreenToClient cannot work when toplevel window is not shown
10:40:06: Debug: ScreenToClient cannot work when toplevel window is not shown
10:40:06: Debug: ScreenToClient cannot work when toplevel window is not shown
(taskcoach:32627): Gdk-CRITICAL **: 10:40:06.648: gdk_visual_get_red_pixel_details: assertion 'GDK_IS_VISUAL (visual)' failed
(taskcoach:32627): Gdk-CRITICAL **: 10:40:06.648: gdk_visual_get_green_pixel_details: assertion 'GDK_IS_VISUAL (visual)' failed
(taskcoach:32627): Gdk-CRITICAL **: 10:40:06.648: gdk_visual_get_blue_pixel_details: assertion 'GDK_IS_VISUAL (visual)' failed
(taskcoach:32627): Gdk-CRITICAL **: 10:40:06.648: gdk_visual_get_depth: assertion 'GDK_IS_VISUAL (visual)' failed