The Sunshine Strategy by Noelle Adams

Britt is used to everyone liking her, and she prefers it that way. She’s a sunny, outgoing person, and she’s good at making other people laugh and smile. The only person she’s never had success with is Nash Coble, her friend’s boss and the owner of her favorite coffee shop.
Nash is a good guy at heart, but he’s also a perpetual grump whose only facial expression is a scowl. Britt’s inability to get him to like her is starting to bother her. A lot. So, encouraged by a challenge from her friends, Britt is on a mission to get Nash to change his mind about her.
She just wants to get him to like her. She has absolutely no intention of falling in love.