Writing to a cell using VBA. Run-time error '1004': Application-defined or object-defined

I am a newbie to excel VBA programming. I am required to build a some complex in VBA which I somehow did.
But my trouble started at the last part where in I am supposed to "print" the values to a cell in excel.

I searched online and found many suggestions like
Unprotect sheet
Activate sheet
supply range
supply sheetname
and few others but unfortunately none of them worked for me. I even tried a simple "Hello World" (as in the attachment) but that failed too.

Would really appreciate a help in this.