4.12.5 editor will not open BP window

After double clicking to open a Blueprint class, I started getting this weird behaviour where the Blueprint editor window doesn’t display. Hovering over the icon in the taskbar gives the result seen in the screenshots, the thumbnail shows the window is open but only the UE4 logo. I’ve had this happen on another previous project file and I thought it was just a corruption with that project, started a new fresh project and the problem persists.
Thinking the problem was installation-wide I’ve verified the engine 4.12.5 installation in the launcher and rebooted windows. Problem persists.
EDIT: this occurs also with opening materials, textures, anything I try to edit now.

Funny solution, may work for you. I was helping a team member over skype with a problem he was having in material editor and suddenly he starting having that same problem. I saw that he was using Norton anti-virus and I suggested he disable it for a min to see if that was it and sure enough everything started working again. So perhaps you need to adjust the behaivor of how your anti-virus handles events triggered by unreal engine like opening swarm or opening a new window.

I use the default Windows Defender on Win 10, turned off real time protection on that for a bit but the problem is the same. After trying out several projects made with different engine versions I only get this behaviour on certain projects made with 4.12, but not all. Still trying to narrow down the situation where the buggy behaviour exists.

Hey , I have had the same problem, all you have to do is go to the taskbar, hover over the BP window , right click and choose maximise. Hope this helps.