This may be due to multiple monitors or screen resolution. In the options, try unchecking "Open Tabs Outliner in the same position and size where it was last closed." Relevant thread: https://tabsoutliner.userecho.com/is/communities/1/topics/519-restoring-a-closed-window-or-tab-fails-when-windowtab-is-50-outside-the-visible-screen-space

How are you supposed to open the options if you can't open TO? Try going back to your multi-monitor setup. If you can't... :-/

The workaround sometimes fails - not sure why yet.

If you use multiple monitors or switch between different resolutions, my thread may be relevant to your interests.

https://tabsoutliner.userecho.com/is/communities/1/topics/519-restoring-a-closed-window-or-tab-fails-when-windowtab-is-50-outside-the-visible-screen-space

Some more programming details, it causes the `window.chrome.windows.create` on line 512 of `treemodel.js` to fail. In particular, `newWindow_chromeWindowObj` is null (because the window failed to be created due to being out of bounds).