Respondus System check
Step 1) Go to the LockDown Browser Help Center (look for the icon in the LockDown Browser toolbar this will look like the letter I(i). Once there, click the button titled "Run System Check." Does running this check produce green check marks for all the tests, as shown below? It's very important that they all pass, especially the "Ports Check." If the Ports Check fails, this is why the "media server" error is occurring.
Step 2) In the LockDown Browser Help Center, click the button titled "Run Webcam Check." Are you able to see your image in the webcam window, then record a video and play it back? If not, then your computer and/or network is blocking the necessary ports.
If so, using a different computer or network may be necessary.