Check for another copy of the editor open. (as said above)
Check for zombie threads in the OS, in Windows via Task Manager - look for dead tasks related to Unreal, not under your active project - close and save again.
Note - these resources may not show on the taskbar.
Hey, I’m fairly new to Unreal Engine, and I’m encountering the same issue. I’m not sure how to resolve it even after reading through the replies. I’ve restarted UE, checked the task manager, and attempted to close any unnecessary processes. I would greatly appreciate some additional assistance. Thank you.