For some reason, I cannot pre-translate a file in Studio 2015 SR2. I use machine translation providers: Enhanced MT (Google), SDL Cloud and MyMemory + my own translation memories. The source file was a clickable technical manual in pdf. I used Abbyy FineReader to convert it into docx. I convert every pdf with Abbyy and never had problems with pre-translate before. This time, however, nothing happened, no segments were filled. I tried using just one MT provider, if I remember correctly, but it also didn't work. Interestingly, SDL Cloud did take away words from my quota every time I used SDL Cloud to attempt pre-translation.
In the end, I gave up on pre-translating and used auto-propagation to quickly insert identical segments.  One more thing: pre-translate did work when I disabled MT and asked Studio to fill empty segments with source text. I'd appreciate if someone explained what could be the problem with MT pre-translation.