hi for me this is globally a bit too flat and it would take you to push the envelope a bit more graphic design wise … there are some efforts in terms of originality but this effort is not being successful enough as u end with something very dense which is lacking breathing and white spaces, definitely too compact if u wish … beware of ranges of colors too as sometimes texts are not super readable and lacking contrast with the background actually … i also regret that there is not a bigger effort in terms of harmony to match with the pictures colors and the theme that u have been opting for …
I think they recject your calendar about quality
i am not sure that this comment will help him lol try to let him know how u feel he can improve it , this will help him more 