If you are attempting to use Unity Remote 5 on an Android device attached to a PC (and perhaps Mac/Linux) but upon clicking Play in Unity you game goes not show up in Unity Remote then these tips might help:
First, disconnect your Android device from your PC and shut down Unity to ensure you’re starting from a clean slate. This walkthrough also assumes you’ve completed the steps found in Unity’s documentation: https://docs.unity3d.com/Manual/UnityRemote5.html
Enable Developer Mode and USB debugging (or re-enable it)
On your Android Device, enable Developer Mode
- Open Settings
- Scroll down to and click About <Device> (Mine says About Tablet)
- Scroll down to the Build Number
- click Build Number many times (after a few times, a message will pop up telling you how many more times to click)
Now that Developer Mode is active
- Go to Settings>Developer Options
- Ensure Developer Options is toggled On (at the top of the list)
- Optional: Enable Stay awake
- Scroll down, under Debugging enable USB Debugging
Now you device should be ready.
- Plug in your Android device to your PC.
- Open Unity Remote 5 on your Android Device
- Open you Unity project
- Click Play
You should see you Unity project on your Android device. If not, try shutting down Unity and Unity Remote and restarting each.