The most common problem with CP violation in the Standard Model is: there isn't enough of it to explain what we see. In short, an extra CP-swapped universe doesn't help solve this, because making matter and antimatter balanced doesn't solve the problem.
The early universe was, at one point, hot and dense enough that matter and antimatter were produced spontaneously as products of the average thermal interaction. As the universe expanded and cooled, it eventually cooled below the temperature at which this is possible. Once this happened, the matter and antimatter in the universe began to annihilate with each other, producing photons as a result.
Suppose physics preserved CP symmetry. This would mean that the hot universe would thermally produce exactly* the same amount of matter and antimatter. So, when the universe cooled below that production threshold, every matter particle would have annihilated with an antimatter particle, and vice versa. After that annihilation event, there would be no matter or antimatter left, and our universe would just be populated with radiation.
Of course, we know this isn't the case; in particular, there's quite a bit of matter in the universe. Based on the amount of matter that we know to exist, and the fact that we don't see any large objects that are made of antimatter anywhere, we can calculate that, before the annihilation event, there was a tiny bit more matter than antimatter - around one part per billion. This imbalance means that some matter was left over with no antimatter to annihilate, and this is the matter that we currently see.
We also know that the Standard Model predicts some amount of CP violation; we can see that matter is produced very slightly more often than antimatter in certain reactions. But the amount of CP violation it predicts isn't enough to explain the part-per-billion imbalance in matter over antimatter in the early universe.
Your proposal is that our universe is twins with another universe where all of the matter has been exchanged with antimatter. But remember how this universe is going to evolve: if it operates under the same physics as this universe, then matter is still going to be preferred in reactions in this universe. In order to get the matter-antimatter balance right after the annihilation event, you're going to have to set this universe up such that it started out with more antimatter. In particular, you're going to conclude that this twin universe is going to start with around two parts per billion more antimatter than matter, while our universe started with the same amount of matter and antimatter. So you're really just kicking the can down the road: you've made the amount of matter and antimatter balanced, but now you have to answer the question: why did the twin universe start with so much more antimatter than matter, while our universe had balanced initial conditions? You haven't really solved anything, you've just changed the unanswered question.
In response to this, you might make the twin universe have different physics than our universe. In particular, you might say that both universes have the same initial conditions, but the twin universe has a version of the Standard Model in which CP symmetry is violated in the opposite way (let's call it the "anti-Standard Model"). So, in the twin universe, antimatter would be preferred to the same extent that matter is preferred in our universe. So now we have one universe with 1 part per billion more matter than antimatter during the annihilation event, and another universe with 1 part per billion more antimatter than matter at that time. This means that the total amount of antimatter and matter, taken across both universes, is balanced. But now you've just got two copies of the original problem: in our universe, the CP violation predicted by the Standard Model is not enough to explain how much matter there is in the universe. Meanwhile, in the twin universe, the CP violation predicted by the anti-Standard Model is not enough to explain how much antimatter there is in the twin universe. So you're back to square one: why does the (anti)-Standard Model incorrectly predict how much (anti)matter there is in the (twin) universe?
*Well, not exactly exactly, if the universe turns out to be finite, but close enough that the difference would be negligible.
