You are using the New Registration Fees Mode. When attempting to purchase a sponsorship (i.e. Gold Sponsor), the following error message appears:
"This sponsorship package includes player/team and it cannot be purchased when you are using Registration Fees as your registrations type."
When using Events -> Registration Fees, you cannot offer sponsorship packages that include complementary teams or individuals. If you want to allow for Sponsorship packages with complementary registrations, you will need to switch from the Registration Fees mode to the Classic Registration Mode. In order to do so, you will first need to delete or deactivate your Registration Fees from Events -> Registration Fees.
Once the Registration Fees have been deleted or deactivated, you can go to Events -> Settings and add the cost per participant and/or group. (You will not see the cost per participant and group options while Registration Fees are active.) This action will convert your registration system back to the old mode which supports registrations with sponsorships.
It may be more simple to remove the included team registrations from the sponsorship package Sponsors -> Sponsorships, under Actions, click Settings - Groups/Teams Included set to blank and manually register your sponsorship teams.
Be sure to run a test on your site to make sure are are ready to take sponsorship registrations.