I have seen the literal translation of the phrase 「つかみどころがない」, somewhere along the lines of being either slippery, vague or elusive. I encountered this phrase
I cannot seem to extend the translation into this sentence. The context suggests that it means the person is kind of hard to talk to (awkward silence), but maybe that's irrelevant for this sentence.
UPDATE: I wrote "literal" translation, but really it's not literal and it's simply the definition given by dictionaries. Apologies for the confusion.