Some organizations have firewall rules in place that prevent the TestProject agent from communicating to the app in the way that it needs to. Check with your IT team to see if this may be the issue. You can also check your computer's firewall settings to make sure TestProject is not getting blocked
If your internet connection is trough a corporate proxy server, and the certificate is self signed, You may need to add the root CA of this certificate to the list of trusted publishers on your computer.
Make sure you have a TestProject agent installed and running on your local machine. If not, you will need to start the agent before you can use it to run tests. If the agent is running, you can try restarting it.
Make sure you do not have any other mirroring software running.
If a new browser instance does not open when you try to run the test recorder for web tests, check that your browser version is up to date.