Try running Steam and the game as an administrator.
Work through these solutions in order. Start with the simplest (restarting) and move toward the most thorough (reinstalling). call of duty infinite warfare steam-api64r.dll missing
Manually cleaning your Program Files (x86)\Steam\steamapps\common folder, or using third-party “PC cleaner” software, can accidentally delete this file. Try running Steam and the game as an administrator