***** Update *****
I have left my original post below intact, but provided amended info in post 2 below, please also read that.

***** Update******

My C420 is no longer recording on the micro-SD card in the hub. The camera gives a live feed, and detects motion and sends alerts, but I have just realised there are no recordings for the last couple of months. 
 

I have just stood in front of the camera, watched myself on the app, received the detection alert on my phone, but there is no recording. 
 

I have checked the settings, and the schedule for the 'faulty' camera shows detection is on 24x7. 
 

In Playback, the calendar shows a few dates in black (which I think is no recordings) but most in blue (which I think means there should be recordings). But the are no recordings on any date and I can't now find and recordings going back to when the camera was installed in January, and I know some were there. 
 

The other camera is recording fine. There is 50% free capacity on the SD card, and looping is enabled. The settings for both cameras appear to be identical. The indicator shows about 35% of the card is used for recordings for the 'faulty' camera. 
 

I feel that I'm missing something obvious but I can't think what. 
 

Any help would be much appreciated. Thanks. 

***** Update *****
see update below. It seems it is a playback issue not a recording issue. 

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