You may need to share access to your Network Solutions account with Thinkspace. If you do need to, Network Solutions has a support article on providing access to us:
https://customerservice.networksolutions.com/prweb/PRAuth/webkm/help/article/KC-347/networksolutions
If you need to share access, here are the contact details:
Contact: Thinkspace
Role: Technical Contact
Email address: domains@thinkspacehq.com