When it doesn't work.

First check that Wing Display is started: the menu bar popover should say "Listening for a signal…". If it says "Idle", click Start. Otherwise it's most likely the network, not the app. Guest, café and hotel Wi-Fi commonly enable client isolation, which stops devices on the same network from seeing each other at all. Discovery has nothing to find. Some home routers do the same across bands or on a guest SSID.

Turn on the tablet's hotspot and join your Mac to it — that bypasses the network entirely and is free. On a network you control, check both devices are on the same SSID and that AP isolation or "client isolation" is off. A USB Connection also sidesteps the network completely and is part of Pro. You can also type the Mac's IP address under Or connect by IP in the tablet app; find it at System Settings → Wi-Fi → Details.

Your Mac is waiting for you. The first time a tablet connects, the Mac shows an "Allow this device?" prompt, and nothing streams until you click Allow. A Deny isn't remembered, so the next attempt asks again.

Look for the prompt on your Mac, click Allow, and connect again from the tablet. Tablets you've allowed are listed under Paired Devices… in the menu bar.

The tablet finds your Mac by looking for it on the local network, and macOS gates that behind a permission it asks for the first time you click Start. Declined once, it is not asked again.

Switch Wing Display back on under System Settings → Privacy & Security → Local Network.

Screen recording permission is missing. The connection is fine; there is simply no picture to send, because macOS is withholding it.

Allow Wing Display at System Settings → Privacy & Security → Screen & System Audio Recording, then quit and reopen the app — macOS often requires a relaunch before a new grant takes effect.

Touch and pen are part of Pro — on Free the tablet says "Touch and pen control are part of Pro." With Pro, the usual cause is the Accessibility permission: video and input are separate grants, so a working picture tells you nothing about whether control is allowed.

Allow Wing Display at System Settings → Privacy & Security → Accessibility. The menu bar has an Open Accessibility Settings… button that goes straight there.

Usually one of these: the cable is charge-only and carries no data; USB debugging is off, or the tablet hasn't accepted the one-time "Allow USB debugging?" prompt for this Mac; Wing Display isn't started on the Mac; the Mac is an Intel model — the USB Connection currently needs Apple silicon; or this tablet has no Pro, in which case the USB tab says "USB connection is part of Pro." and has no button to connect over the cable.

Swap in a known data cable, turn on USB debugging in Developer options, click Start on the Mac, then unplug and replug and accept the prompt. Cables bundled with power adapters are the usual culprit. On an Intel Mac, connect wirelessly for now.

Your Mac checks the subscription each time the tablet connects, using the purchase record Google Play gave the tablet. The tablet says which check failed.

The tablet remembers each Mac it has paired with. After you reset the Mac, use a different user account on it, or remove Wing Display's keychain key, it looks like a different computer.

Tap Forget this computer on the tablet, then connect again and click Allow on the Mac.

The Mac host and the tablet app are on versions that don't speak the same protocol.

On the Mac choose Check for Updates… in the menu bar; on the tablet, update Wing Display in Google Play.

Wing Display adds the tablet's display to your Mac when you click Start, before any tablet connects, so the pointer and windows can wander onto it.

Connect the tablet, or click Stop in the menu bar to remove the display. System Settings → Displays lets you place it where you expect.

USB-C negotiates which side supplies power, and some Android tablets can settle on feeding the computer instead of drinking from it — often after a prompt like "Charge connected device". The tablet then runs its screen off its own battery while charging your Mac.

Check the USB notification on the tablet and set it back to charging. If the setting won't stick, restarting the tablet reliably restores it. Worth watching on long wired sessions.

Wing Display pauses while the Mac sleeps and recovers on wake. If recovery fails, the menu bar popover says "Recovery failed".

Click Retry in the popover.

Wireless contention. A busy 2.4 GHz band, distance from the router, or neighbours sharing your channel all cost you frames — and a shared network can degrade at any moment without anything changing on your side.

Move to the tablet's hotspot — free, and usually enough, because it takes you off the contended network altogether. If it is still not clean, the USB Connection carries far more than Wi-Fi and is unaffected by anything happening on the network; it is part of Pro. Wing Display keeps separate quality settings per connection type, so tuning the USB Connection won't disturb your wireless setup.