Just as many men ejaculate quickly, there are men who are unable to ejaculate when they choose to do so but there are techniques to help and enable penetrative ejaculation to occur easily.
Some can ejaculate during masturbation but not during penetration. This also has implications for fathering a child – but can be resolved.
One simple trick is to jel charge a regular thickness condom. This enhances sensitivity but removes the inherent danger of pregnancy, thereby reconditioning the man to enable penetrative ejaculation again.
This can work well, especially if the woman is using additional reliable contraception.