My Mac camera or microphone is not working
Solution 1. Try logging in with another compatible browser, check for the list here.
Solution 2. Allow your browser to access your computer's Mic/Cam
If resetting the system environment doesn't solve the problems you can try the below items to resolve the issue!
MacOS 10.14 (Mojave) or above
In MacOS Mojave, Apple has introduced some system-level privacy controls for your mic and camera. These are great for privacy, but it is possible that your browser was mistakenly blocked from accessing your mic and cam. You can check on this and allow your browser to access your mic and cam from the Security & Privacy section in your System Preferences. To access these settings, do the following:
Click on the apple in the top left > select System Preferences

Click on the Security & Privacy section
Click on the Privacy Tab
Click on Camera in the list of options, and tick the box next to the Chrome browser to allow access

Repeat step 3 for your Microphone
After doing this, restart your browser for the updates to take affect
MacOS 10.13 (High Sierra) and earlier
If you use an older version of MacOS, there are no system level controls for your camera, and instead MacOS will default to the settings on the application level. However if your mic selection isn't sticking, there is a system level control of your mic. You can access this by clicking on the Apple in the top left corner of the screen and selecting System Preferences. From here, click on Sound and then select the Input tab. This area will list all input devices that are available, set the device you would like to use for Input.

Solution 3. Confirm the Mic/Cam settings for your browser
Google Chrome
Mic and Cam defaults can be accessed in a number of ways in Chrome, but the easiest is to paste the following links into your URL bar:
Cam: chrome://settings/content/camera
Mic: chrome://settings/content/microphone

From these areas, you can manage the default cam/mic for Chrome, and also whitelist or block websites from accessing your cam/mic! For the smoothest experience, you'll want to have Remo listed under the Allow section.
Safari Browser on Mac
For the Safari browser you can also allow mic and cam for Remo.co to do this in the Safari app on your Mac, use Websites preferences to customise how you browse individual websites. To change these preferences, choose Safari > Preferences, then click Websites.

Go to invite link that was sent to you and prior to logging perform the steps below.
Click on Camera on the left sidebar and add remo.co and select allow.
Click on microphone on left sidebar and add remo.co and select allow.
Confirm audio inputs and outputs
If your computer has multiple screens or you use different audio devices to record or listen you may have selected a different audio input or output and need to pick the right one to work with your browser and Remo.
Select the right audio input and output by click on on the top left three dots or lines to pop open the sidebar settings.

Select the correct camera and microphone input for you to use.
Solution 4. MacOS - Check for Audio and inputs and Outputs
You also need to check that the right audio inputs and outputs are selected in the settings.
You can access this by clicking on the Apple in the top left corner of the screen and selecting System Preferences.

From here, click on Sound.

Click on the Output tab and select the right output option.

Click on input and select the Input you want. You can also check if the input is working checking the input level as you talk. If the bars are moving then your microphone is working.

Updated on: 01/05/2020
Thank you!