In both Firefox and Thunderbird, I have this problem where the toolbar/ribbon disappears completely. Only the content of the active tab is visible. In Firefox, when I try to close the window via the Windows task bar, I get a question whether I want to close all open tabs (but they are not visible, only the active one is.) I found a reset button to reset add-ons and settings, after which I can reuse Firefox until the problem happens again (https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings#). In Thunderbird, I only see the content of the current email, no tabs, no ribbon, no way to get to the folder structure (where the Inbox etc. would be shown). For now, I have switched back to Outlook, although I'd rather not use it... I have tried to click or right-click on the white space where the ribbon would normally be, hoping that the icons would only be hidden, but still clickable. But when I do that, I instead activate the window underneath it (until I have closed them all and there is not window underneath anymore.) I have read that there can be issues with tabs when the window is maximized, but I cannot reduce it since the "-" symbol is not displayed. Is there a keyboard shortcut or an F-key combination that will reduce the window size (i.e. get out of "Maximized" mode)? maybe that might help. In case I get disconnected, could you please also provide info as to how to get back to this topic? Thank you! Sibylle