I am very new to Anthias, but I think this is a discrepancy between the set start time on the web portal and the internal time on the raspberry pi.
Check your date (and time) with (CTRL+ALT+F1 to open console):
date
If the time of your web portal is different to the shown time, update the time with:
date -s "YYYY-MM-DD HH:MM:SS"
…and your content should show up.