Landscape reverting to black when I let the left click go while texture painting

Hi all,

I am trying to work on an open world game right now, and texture painting the landscape. The issue is that I have been able to texture paint half of it, but with the other half, when I initially paint it it renders, but on letting go of LMB, it goes back to black (the material instance). Any suggestions on solving this issue? Thanks. Here is an image: