I have a new Flex sensor which I just installed yesterday that seemed to setup fine, connects to wifi with a good signal, registered, and seems to send data for a couple of minutes and then appears to go offline. If I power cycle the device it connects again and sends an update but stops doing so after a couple of minutes. It does seem to continue to broadcast the PurpleAir-xxxx SSID even after it’s connected, but doesn’t allow any devices to connect to it. I’m on a Unifi AP mesh network and a UDM Pro router with dozens of other devices with no issues.
PS. How do you set it up so the Purpleair setup wifi has a password set up? Seems like a critical vulnerability in 2023 to have a device broadcasting an insecure hotspot!