If the buds do not open, the weather is usually to blame
In particular, rose varieties with double to very double flowers tend not to open them or not to open them completely. The reason for this is usually to be found in the weather: If it is persistently damp and it rains frequently, the outer petals cannot dry out and gradually rot. Persistent moisture favors an infestation with gray mold (botrytis) or powdery mildew, which preferentially attack young shoots and flower buds. In addition to too much moisture, the cause can also be found in excessive dryness as a result of a strong, prolonged period of heat.
If, on the other hand, the weather is right and your rose shows no other signs of illness, it may just be in the wrong location. Implementing it often works wonders.
Roses should never be fertilized when they are planted, but only when they have established themselves in their new location. Fertilizing too early may prevent the rosebuds from opening.