You may need to switch to a different browser, like Google Chrome or Mozilla Firefox. The Safari browser that comes with OS may not able to redirect you to the download page.
Here's the download link for your reference. You need to download an older version (v9.x) of TeamViewer QuickSupport. When you try to run the current version (v13) of TeamViewer QuickSupport, you will receive the following message. Here are the steps to setup TeamViewer QuickSupport on an older Mac. So, if you're still running an older version of Mac Operating System(OS), you need to run an older version of TeamViewer. As of, the current TeamViewer (version 13) only supports OSX 10.10.5 or later.
In some cases, we may need to remotely access your system to troubleshoot the issue(s).