Blank graph

Hi, My previously working card has stopped displaying any information and looks like so:  The code behind it is: ``` type: custom:history-explorer-card graphs: - type: line entities: - entity: sensor.bedroom_1_temperature_and_humidity_sensor_4 - entity: sensor.bedroom_2_temperature_and_humidity_sensor_3 - entity: sensor.bedroom_3_temperature_and_humidity_sensor_2 - entity: sensor.bedroom_4_temperature_and_humidity_sensor - entity: sensor.thermostat_temperature - entity: sensor.weather_station_temperature ``` Do you see any issues with that is defined? Many Thanks