Programming/editing drums - won't let me see the pattern

Probably very basic as I am new. Managed to program 2 bars of drum pattern through Groove Agent SE4, played it back, pretty nice, went back in to edit a couple of things and it just showed the drum editor as blank, even though on the loop, the sound of the drums is coming out. I have gone back out and tried to re-enter the section a few times but can’t get in.

Am I doing something wrong (I assume so). Any advise appreciated. As well as any tips for programming drums easily. (I am new to cubase, but not to music writing!)

Thanks in advance.