After days of debugging here are my findings:
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There were changes done to HUD Controller logic - although Verse now gives warning for using previous logic of hiding HUD Controllers (i.e. using function ‘.HideHUDElements()’), there are still no warnings or errors given during validation if you have placed ‘HUD Controller Device’ inside your ‘Outliner’/game map. Deleting HUD controller allows users to connect to the island hub when launching (the small box with trees and patterned blue floor) - without this change, Fortnite window would not even get that far with loading you to your island.
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I randomly stumbled on THIS bug report - people seem to be experiencing problems with textures larger than 1024x1024. I remembered that after UEFN update on 08.04.2025 it was giving me warnings regarding imported texture dimensions, so I decided to test this out.
Validation gives no dimension warnings regarding this after you change imported textures to 2048x2048, but unless you downgrade them to 1024x1024, your session would not launch successfully, resulting in infinite “Loading..” screen until it eventually reaches hearbeat after 600 seconds and crashes Fortnite window.
I do believe UEFN should allow textures at least in dimension 2048x2048, as 1024x1024 makes textures appear blurry and non-polished. -
After these changes, I was still unable to connect - now clicking on ‘Launch session’ started showing “Exit session” (as if I should have the project up and running). I am also not the only one that faced this problem, as also mentioned here.
I discovered a workaround regarding this - if you launch Fortnite before opening UEFN and then click later ‘Launch session’, this resolves this problem. I was finally able to connect to my project, yay!
So, why is this happening? After digging through Fortnite logs, it seems that there has been some major change regarding session validation and launching to your project after UEFN version 34.20 was released. Local project validation and what is happening on Epic’s side seem to have some drastically different requirements, which causes a wide variety of problems for different users.
Please let me know once this information has been forwarded to relevant parties. Thank you!