If you have Fortnite with the Editor Not Connected message, and in UEFN the memory calculation is runnind (the animation is spinning).
Do not cancel the Memory Calculation, instead try this, without closing Fortnite, launch a session again, it should connect and then finish the calculation, if you are the lucky ones, it will not freeze in the end and you will get the report.
If you are in team Freezed UEFN, create a new map and move your assets in groups and do Memory calculations in your second map until it freezes, then start deleting the latest moved assets until find which one might be the issue, when you got a suspect, try to replicate in your original map, hopefully will recover your memory calculations and enable you to publish.
Please share anything that you find that could help us fix this issue as a workaround while we are waiting for a Patch.