Hello there We have read the question We try to help you. In the profile folder/map. If you have set up or having that file the file the parent.lock in your profile folder, you can see it as leaving and starting up your Thunderbird software, that it is restarted /closed every time, because running these parts of data in or off this process, this software Thunderbird sometimes unfortunately cannot start itself, there are also other issues that can show these causes as described. You can if you like follow these steps and erase and delete them .so after that this process and steps ,the program can restart itself again. In the same profile folder, try to delete the following data: parent.lock old parent.lock session.json xulstore.json Is it possible to do that? So we can solve that issue of you re computer pc? Greetings firefoxvolunteer