If the domain is squatted, didn't the squatter have a contact link? Their business is usually selling domain names after all. Maybe the squatter is using GoDaddy's anonymity service as a way to filter prospects not willing to pay money to reach them.
What you can try is go via GoDaddy again and increase your offer. Or another mediator, e.g. https://sedo.com/us/buy-domains/domain-brokerage/. If you're not willing to offer more money or the squatter doesn't want to sell then move on (choose a different name).