What are the biggest hurdles when trying to sell to big corporations?

Time. The sales cycle for large companies is much longer. Depending on the size and scope of the org you may be looking at weeks, months, or even quarters

Learning their purchasing cycle: budgets get locked in or they aren't allowed to buy something at that point in time.

Finding out what their real needs are: you think you're solving a problem, but they probably don't need your specific solution, or at least they don't know they do.

Who has decision making power: usually the person/team you are pitching isn't the one who approves the purchase. So empowering that person/team to go to their managers and get approval is important. Give them ammo to enable them to sell you internally.

Getting in touch with decision makers