have you checked your firewall and anti virus programs. I really think the problem is external to Thunderbird.

The windows 10 firewall public/private is off. windows defender is not known for blocking tb. both FB and TB work in a win10 fresh install, but not the upgraded version. FB and IE11 both fail to connect to the router.. chrome and edge ok. hosts and lmhost files would affect everything.

I have no idea about windows 10. but it IE can not get out there is a very good chance there is a DNS issue. and that is not hosts or lmhosts.

Given that Thunderbird site on the same Geko engine as Firefox. they will both suffer the same problem.

have a look hare https://www.youtube.com/watch?v=iQdU763UsBk at the 6:56 point and check the ipconfig entries to see if you have a DNS server registered and a gate way.

DNS could be an issue since the gateway is not in DNS.. you know.. the infamous 192.168.1.1? Cant open the router. So it would seem that data is not making it from layer 7 to layer 1

Problem revealed and solved. Hijackthis reported that Speedbit Video Accelerator has 6 or more LSP entries in the stack. Once I uninstalled Speedbit, the entire chain was cleaned up and upon reboot Bing updated my wallpaper. Oh and IE11 etc. now work.