I need help..

It's been a while I was away from BD2 so let me just cut into the point: I was doing my game preference things on DB2 and when I going to start a new map, this appeared:

maybe I am an idiot for missing something since it's almost half a year I'm not using DB2. so yeah, a little help here please?

https://forum.zdoom.org/viewtopic.php?f=44&t=54957

Do you know there's a bugfix version of GZDoom Builder? It probably fixes some of these things.

Doom Builder 2 is discontinued. Get the one in the link that Glaice put...it'll solve all your problems

You're not the first person to have this happen. Here is an old thread about this very thing. Though it would be good if you did update to GZDoom Builder.