Been having a problem booking awards out of Croatia to the US for next summer. Availability shows up for multiple days and airports on united.com (not mixed cabin segments), but when attempting to book through lifemiles every single day shows up as sold out. When removing the first Croatia leg the later segments from say MUC-JFK or VIE-JFK show up without a problem.

Is there a known issue with the Avianca website on booking flights out of there? Would calling in (ugh) help the situation, or does the website availability mirror what agents see?