Make sure your Wi-Fi is working properly by using another device connected to your Wi-Fi network.
Check whether you have correctly remembered and entered your own Wi-Fi network password when connecting the AeroCount particulate matter detector to your Wi-Fi network. (For example, by forgetting the network on your computer/laptop/phone/tablet and reconnecting to your Wi-Fi network.)
Restarting the modem may fix this problem as well. Additionally, some people have more success by using a laptop rather than a mobile phone. Follow the next steps to restart your modem (source):
Unplug the power and Ethernet cables from the modem. Some modems have backup batteries that need to be removed too.
Wait 2-3 minutes for the modem to fully power off. All the lights on the modem should be off.
Reconnect the power and Ethernet cables to the modem.
Wait for the Internet light to turn solid, then check if the internet is working properly.