Picture but no control, freezing, or a black screen: a diagnosis order

Almost every remote session problem falls into six shapes, and the shape tells you the cause. Working through them in order beats changing settings at random, which is what most troubleshooting turns into.

1. Picture arrives, taps do nothing

The single most common confusion, and it is not a connection problem at all. Video arriving proves the connection is working perfectly. Input needs a separate and much stronger permission on the device being controlled — the accessibility service.

Fix: on the controlled phone, Settings → Accessibility → Installed services → enable the app. If it is already on, turn it off and on again; it can end up in a state where it is listed as enabled but not actually running, particularly after an app update. See the accessibility permission.

2. Part of the screen is black

That region is protected by FLAG_SECURE — the app has told Android it must not be captured. Banking apps, payment screens, password managers and DRM video do this. It is not a fault and no remote tool can work around it, because Android enforces it below the app layer.

Fix: there is none, and that is correct. Work around it by describing what is on the screen, or by doing that part yourself.

3. It worked, then froze after a minute or two

Classic battery-optimisation kill. The sharing app was stopped by the system, usually after the screen went off or you switched apps. No error appears because nothing failed — the app simply stopped existing.

Fix: exempt the app from battery optimisation, lock it in recents on manufacturers that offer that, and keep the screen on during a session. Full detail in why Android keeps killing the app.

4. Blocky, smeary picture whenever anything moves

Bandwidth, not a bug. The encoder is being asked for more bits than the uplink can carry and it drops quality to keep up. The constraint is the sharing phone's upload, which on mobile is usually a fraction of its download.

Fix: move the sharing phone to Wi-Fi, closer to the router; lower resolution if the app allows; close photo backup and anything else uploading. See what a session costs in data.

5. Everything is late but sharp

Latency rather than bandwidth, and the two need opposite fixes. A sharp picture means the encoder has enough bits; the delay is in the path.

Fix: check whether the session is being relayed rather than direct; try one side on a different network. If the two devices are far apart geographically, there is a physical floor you cannot get below — see why the remote tap lands late.

6. It will not connect at all

Work through it in this order, because the first two are the most common by a wide margin:

1. Which phone is showing the code? The code belongs to the sharing device and is typed on the connecting one. People routinely do this backwards.
2. Is the code fresh? Codes are usually tied to a live session. Have the other side start again and read the new one.
3. Is the app still running on the sharing phone? If it was closed or killed, the code refers to nothing.
4. Try one side on mobile data. If it connects there and not on Wi-Fi, the network is blocking it and nothing on the phones needs changing.

Full detail in why the two phones will not pair.

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