Fixing Google Chrome Microphone Permissions on Desktop
Try simply refreshing the page first and see if the pop-up then appears.
Otherwise, click on the three-dot icon in the top right-hand corner of the screen and choose "Settings".
The Settings screen will then appear, and from here, click "Privacy & Security" on the left-hand side, then "Site Settings".
Scroll down until you see the section for "Permissions" and choose the "Microphone" option.
First, check and ensure the option for "Sites can ask to use your microphone" is enabled.
Next, if the microphone permissions were blocked, you will see under "Not allowed to use your microphone" the Caption.Ed website. Click on the play icon, find the Microphone option, and change this from "Block" to "Allow".
Note
Alternatively, you can click on Reset Permissions, and then you refresh the browser. It will provide you with the pop-up to allow permissions.
Once you have reset the permissions, go back to Caption.Ed and refresh the page. You can then select the microphone you wish to caption from.