So another alternative might be

=AVERAGE(IF((MOD(COLUMN(B6:J6),2)=0)*(B6:J6>0),B6:J6))
committed with CTRL + SHIFT + ENTER

But the below works fine for me...

=SUM(B6,D6,F6,H6,J6)/MAX(1,(B6>0)+(D6>0)+(F6>0)+(H6>0)+(J6>0))