When you have 'Not only' at the beginning of the sentence, this has to be followed by an inversion of the verb and object, just like in the question form. For example: 'Not only is he a talented sportsman, but he is also a fine musician.' And, just as with question forms, when you have a verb in a simple tense (such it 'It knows), you need to use the auxiliary do/does/did. Not only does each object know ... [Not only] + auxiliary verb + subject + main verb

"does" / "did" / "will" show the verb's tense ("know") in your example. `not only` <VERB> _____ `but also` _______ is a standard English phrase. `not only does` _____ `but also` ______ : PRESENT `not only did` ______ `but also` _______ : PERFECT `not only will` ______ `but also` _______ : FUTURE `not only will` __ `have` ____ `but also` _______ : FUTURE PERFECT Examples: 1) "not only does the cat sleep, but also it sleeps" 2) "not only /did/ each object know it was being logged, but also they /updated/ their status" 3) "not only will we build schools, but also we will help families." Notice that in 2) "did" and "updated" are both in the perfect tense. Don't mix verb tenses here. I will understand but, it will sound awkward. Some people switch and "also": "not only does the cat eat, but it also sleeps" Some people remove the pronoun: "not only does the cat eat, but also sleeps." Both are fine to me, this sounds more colloquial.