While individuals in the corporation, including the CEO, may be deeply committed to the idea of corporate charity, and even to your organization, they must also balance other demands. Show them how they do well by doing good. The fact that you are a good group that needs money, and a gift to you would be a tax deduction, describes you and thousands of other nonprofits. It is meaningless to a corporation. The fact that you can open up a market for their products, or give them some positive publicity, or make life easier for their employees, or help guarantee a literate workforce, or eliminate problems caused by drugs, alcohol, or domestic violence is meaningful to a corporation.
Many corporations make non-monetary contributions, which are often easier to get than cash.
Corporations will often give their old desks, filing cabinets, computers and computer tables, chairs, and so forth. If you see a corporation redecorating, ask them what they are doing with their old stuff. They may be more than happy to have you haul it away. Some corporations donate the products they produce. Food and beverages are often free to special events, but more expensive equipment can also be obtained.