It will stop working if your registry entries are corrupted, but this is very unlikely unless you’ve been fiddling with the registry yourself. If you’ve just deleted Todoist in order to reinstall, then consider the reasons why it stopped working. Here’s a link to the Windows installer troubleshooter, and here’s a link to Apple support for Mac problems. If your default uninstaller isn’t working, then it’s something you need to fix with the publisher of your operating system.
Uninstalling is done through the default uninstaller on your device, or through the Microsoft Office platform.
