A friend of mine booked SFO to DEL with a 3- night stopover in IST.

When he goes online to the page which should allow him to book his free 2-night hotel, after he checks the box for his name and that of his travelling companion, selects double room, he gets this message "your room type and passenger choices are not compatible"

Any ideas as to why he is getting this message, and how he can book the free hotel?