WiFiSSLClient will not connect to servers with LetsEncrypt certificates I'm trying to send data from an Arduino program to an app running on Google App Engine but WiFiSSLClient.connect() always returns false.

This is despite


the server being up and running;
the code working when the web app was on a different server.


The only possible explanation I can come up with is that the App Engine app uses a LetsEncrypt certificate while the other server was using one by another company.

WiFiSSLClient client;
if (client.connect(server, 443)){
    // Connected to server
} else {
    // Failed to connect
}


Does anyone have any solutions to this problem? I had a look at WiFiClientSecure; it has the ability to set the CA certificate in code but this seems like a bit of a pain.
The solution is to update the certificates the WIFI 101 Firmware Updater tool (in the Arduino IDE).


Install the FirmwareUpdater sketch, as described on the Arduino site.
Select Tools -> WiFi 101 Firmware Updater. Click on the Add domain button at the bottom, enter your domain and click Upload Certificates to WiFi module.

Upload the sketch to your Arduino. It should now connect to the server.