Homology modelling of protein with two identical subunits in its quaternary structure
For anyone who will struggle with this problem in the future: The trick is in reading WHOLE of the manual, NOT submitting the whole sequence/badly segmented sequence, and in NOT attempting to input the same subunit twice. It is necessary to upload subunit FASTAs separately as a hetero target, and each subunit ONLY ONCE (so A,B,D,E for A-B-D-A-E receptor), and then search for templates: most probably there is a template with your quaternary structure uploaded somewhere already, and if not, you can choose preferred arrangement afterwards.