Elias here with Shopify Support. Thank you for reaching out.
Sorry to hear that the 'Contact us' link isn't working on your order confirmation page. The link for the 'Contact us' comes from the sender email used in your General settings, so you can change your email address there. However, this link is controlled by the secured checkout and, with the exception of Shopify Plus stores, accessing the checkout coding is restricted. That being said, I do need to ask a couple of clarifying questions to help troubleshoot the issue. Does the issue only occur on one browser? Or, is the issue persisting across different browsers and devices?
If the issue is only happening on one device, then you can try clearing the browser's caches or resetting the browser. However, if the issue persists across multiple devices, then our Technical team would need to take a closer look at your account. Though I'm unable to take a closer look at your account, as we're unable to provide account-specific via the Community Forums. However, our Support team would be happy to assist you through live chat, email, or callback. To start a support request, please visit the Shopify Help Center and log in to your account.
I hope this points you in the right direction to get support with the link, and I'd also love to know what might be causing the issue. Keep me posted!