The fiscal sponsor must be a 501(c)(3) organization as recognized by the IRS. The fiscal sponsor cannot be an organization whose tax-exempt status is pending. The sponsored project must be able to qualify for exemption under section 501(c)(3), even if the project has no intention of ever applying for it.
Pressing the Ignore button on the listed invitation on the LinkedIn site is effectively a soft rejection. The message then moves to your Archived folder. You can later choose to open the message again and accept the request.
Look at the gray button next to the person's name. If the button reads Friend Request Sent, the person has not yet accepted or declined your friend request. If the button reads +1 Add Friend, the person denied your friendship request. Tips: I suggest before sending friend request. You may send a message and explain yourself in short MSG.