There are many factors that cause the disconnection, when you meet the connection failed, you can follow the troubleshooting guides to see if it works.
1. Check the network condition of your device.
2. Keep WLAN always on during sleep.
Open Settings on your device > WLAN > Advanced > select Always of Keep WLAN on during sleep option.
3. Turn off the Power saving mode
Open AirDroid > Me > Settings > General > Turn off the Power saving mode
Xiaomi, Huawei, HTC, LG, Sony, Google Nexus specific settings Click Here
4. Keep AirDroid running on the background.
AirDroid process may be killed by some systems after a long period of inactivity, please kindly restart AirDroid to activate AirDroid process.
5. Check if you've installed some app manager or memory cleanup tools that might kill the AirDroid process.
AirDroid process may be killed when running memory cleanup feature. Adding AirDroid to the Memory cleanup whitelist will help.
6. Keep enough systems manage memory and battery when connecting to your device.
7. Unlock your device and keep the screen awake when connecting to your device.
If you want to keep the connection all the time, keep the screen always on will help.
Open Settings on your device > Lock screen & password > Sleep >select Never
8. Try Lite mode
You can try Lite mode if your device and computer are on the same Wi-Fi network and the IP address shown in AirDroid on your device.
iOS device only supports to be connected under locate connection, the remote connection is not supported now.
If the above steps can not solve your problem, and you have already know the reason, follow the link(s) below to find the settings according to your need.