Diễn đàn hỗ trợ Firefox

My previous post seems to have disappeared, so will try again. I am 85 years old and have been using Thunderbird fo over 15 years with out any problems. Afew days ago I tried to send an e-mail and didn't have any "Send" button. In trying fix, I some how deleted my contacts sidebar. I sill have my addresses book. I have tried everything to retrieve them but no luck. I tried removing Thunderbird and reinstall, but it comes back the same. I would appreciate an guidance in trying to resolve my problem. Thank You

Each time I open Thunderbird, Firefox randomly switches to another window. When I set Firefox back to the proper window, Thunderbird closes.

Using Windows 11, Firefox 130.0.1 and Thunderbird 128.2.3esr.

I suspect the problem is with the latest release of Thunderbird. I want to install the older Thunderbird 115.10.1, but I did not find an easy way to do that.