I cant generate a dead load (floor load)

Hi! I would like to ask for some help. I am experiencing this problem where I cannot add a floor load to my work. Every command that I attempt to generate always end up with an error message. I already checked of duplicates of notes, beams and structures but none. I also checked the accuracy of the coordinates that I put but I still cant generate the dead loads that I want to add. Here is the file of my work. I will wait for any response. Thank you so much!

3225.Three-Story Residential Building.STD