Hey there,
I am playing around with an Arduino MKR Wifi 1000 using the IoT Cloud and a 16x2 LCD display. I setup a fresh sketch and only can get the display to work when commenting out the IoT Cloud-related lines. In a "normal" sketch it works like a charm. I do not not what to do 
BTW I followed this tutorial: https://create.arduino.cc/projecthub/Arduino_Genuino/displaying-messages-sent-from-iot-cloud-on-an-lcd-1e6f32