Blue Harbor Billionaire by Declan Rhodes

Billionaire tech genius Ronan Gallagher is a master of algorithms, but a hopeless nerd in matters of the heart. When a mysterious safe-deposit box in Blue Harbor drags him away from his code, he doesn’t expect to meet Tyler, a charming history teacher and baseball coach. Tyler’s life has revolved around coaching and teaching, especially after losing his best friend to cancer. But Ronan’s arrival disrupts everything, stirring up feelings Tyler never expected.
As Ronan and Tyler team up to crack the box’s secrets, their scavenger hunt leads them on a wild chase through Blue Harbor’s hidden history, and soon, Ronan’s company demands his return.