I’m having same exact problem
"Failed to find a server through matchmaking: Error: errors.com.epicgames.fortnite.invalid_region
Your backend is: Fortnite
Your Build is: ++Fortnite+Release-36.30-CL-44367537
Region: NONE
BuildIdOverride is: 43760582"
I did not change a thing in my project. Issue started happening after last update.
Managed to fix that. After veryfying UEFN and Fortnite files failed to resolve the issue I reinstalled UEFN. Then I launched Fortnite and played a creative map to acquire region settings. After that I closed Fortnite, launched UEFN and I was finally abled to launch an edit session succesfully via editor.