In romance writing, there's this little thing called the Big Miz. It's a bad thing. Lord Lovem-n-leavem marries Virginia Vicarsdaughter for some strange reason. They fall in love. And then one day Virginia sees Lord L&L groping the chambermaid. She packs her bags and leaves, never to return. Lord L&L vows to hate all women because Virginia, that cruel minx, left him all alone and unloved. She used him. She never loved him, and he knows this because his cousin, I. Wantthetitle, told him so. Then, of course, the lord and his wife are reunited, reluctantly, and spend 350 pages hating each other because of the transgressions . Eventually, the veil falls from their eyes when they have a conversation (ha, never!) or when others who are in the know reveal the truth (she always loved him and he was only helping the chambermaid because she'd darn near fainted as he was innocently walking by). Happy Ever After.
However, misunderstandings do have their place in romance writing (heck, in any writing I suppose). It's the Mars/Venus thing and it lends potential for a real misunderstanding. Characters can talk at cross purposes which can lend to the conflict. By no means should this be your only source of conflict, nor should it be so overused that the hero/heroine are always misunderstanding one another and getting mad. That can lead to Fight/F*ck melodrama, which ain't pretty either.
But a good misunderstanding of what the other is saying can lend to the drama and characterization. For instance, the heroine's talking about the time six years ago when the hero stood her up for a date, and he's thinking she's still mad, and she's just wanting him to say why he did it because he never told her the reason, but he's thinking he'd better not say anything because that'll only make her madder, especially when she finds out he overslept since he's CIA and she probably thinks he was rescuing the free world or something. (Bad example, but it's late and the brain isn't working so well.) 🙂 People don't always say what they mean or ask what they want.
What I mean is that one character can be talking about something, or doing something, and the other character has a definite impression of why and what he should do in turn. But he's wrong about it, and the character talking or doing only gets more frustrated. The cycle continues until one of the characters sees through this. Now you have an opportunity to move the relationship forward, even if only a fraction, because understanding builds closeness.
In summary, have them talking or doing at cross purposes, have one of them achieve understanding and reach out to the other. Bring them closer. Don't overdo or it gets ridiculous. Just think of the Mars/Venus moments between you and your SO/spouse and you'll know what I'm talking about. 🙂