Selecting Areas of Standard Reflectance

Hello,

while trying to generate a multispectral image, I’m running into problems selecting the region of known reflectance. Every time I try to select the area of 95% reflectance, it doesn’t show the selection box and this doesn’t let me select the area?

im not sure why it’s not working as it has worked in the past, is there any way to fix this?

thanks again,

nic