This only happens for me if the relationship text you're using isn't actually the correct relationship text - so I would double-check that.
I just tried this myself to double-check (10.4.5) and it works fine for me (I used a basic setup of entity A = "the parent", entity B = "the child" containing relationship text from A to B = "all instances of the child for the parent").
If I had to guess (and I'll have to since you can't post your project) I'd say that it was probably a normal quote mark in the relationship definition text and a smart quote in the word document (possibly but unlikely it could have been the other way around).
Since they're different characters the compiler wouldn't recognise them as being the same so different text = no relationship text in conclusion line of table = the error message you saw.
It's one of the reasons why there is the recommendation to remove the automatic smart quotes feature in your word setup (see the help topic on setting up to write rules in Word):