No, there are no planets on the "other side" of the Sun that we cannot see due to the Sun being in the way. The concept of planets being permanently hidden behind the Sun is a common misconception.
The orbits of planets in our solar system are all confined to a relatively flat plane known as the ecliptic. This means that from Earth's perspective, we can observe planets along a particular path in the sky, which is generally close to the Sun's apparent path throughout the year.
As the Earth orbits the Sun, our view of the sky changes. At any given time, the Sun is only in the way of observing a limited portion of the sky, roughly within a few degrees of its position. However, as Earth continues its orbit around the Sun, different portions of the sky become visible, including the regions where the planets are located.
Therefore, while there are times when the planets may appear close to the Sun in the sky (resulting in challenging observations due to the Sun's glare), they eventually become visible in other parts of the sky as Earth continues its orbit. Observations from different locations on Earth, as well as space-based observatories, can also help in overcoming the limitations posed by the Sun's position in the sky.
In summary, there are no permanently hidden planets on the other side of the Sun. The planets in our solar system can be observed from Earth at various times throughout the year as the Earth orbits the Sun.