Both male and female sexual dysfunctions can contribute to unconsummated marriages/relationships. Here are some examples:

• Vaginismus occurs when a woman’s pelvic floor muscles contract involuntarily at the start of penetration. This contraction makes the vagina tighter and narrower, making penetration (such as with a penis, finger, or gynecologist’s speculum) becomes extremely difficult or impossible. 
• Erectile dysfunction (ED) occurs when a man is unable to get or keep an erection rigid enough for penetration. ED may have physical or psychological causes.

• Premature ejaculation (PE) occurs when a man ejaculates before he wishes it to happen. Severe PME may lead ejaculation before penetration.
• Couples can have difficulties consummating their relationships for a variety of other reasons:
• Anxiety: Couples who have little or no sexual experience may feel anxious about their first intercourse. They may not know what to expect or worry about their performance.
• Insufficient sex education: Partners may be unfamiliar with sexual anatomy and the sexual response cycle, especially if they have never been in sexual situations before.
• Fear of pain:  People may expect intercourse to be painful. For some, this fear may be the result of insufficient education. Hearing stories about painful first intercourse experiences can add to apprehension, too.
• Taboos or negative feelings about sex: People who have grown up believing that sex is “bad” or “dirty” may have trouble consummating their relationships.
• Societal pressure: In some cultures, couples are expected to consummate their marriages within a certain period of time, and families might require proof that consummation has taken place. In others, couples may feel they are supposed to have sex within a certain time frame, regardless of whether they feel ready to do so.
• A sexual secret: People may have an undisclosed sexual orientation or preference