i hate to puta downer on things but my corys lay eggs quite often - ive never had any fry from them tho - maybe the makes are firing blanks or something
if you want to 'encourage' them to spawn - a water change with the newn water being a few degrees lower than the tank is known to stimulate them - replicates rainfall i suppose
other ways to increase the odds include using amazon sword plants or flat pieces of slate n boggy leaned nr the glass - the corrys will still lay on tank glass but the items make it harder for the others to get to the eggs and ive noticed if other fish cant see eggs easily, the eggs are usually safe
fish are like pigeons - it only takes 1 to find food for all of em to join in
pimafix (quarter dose) protects against fungal problems too and upping the airflow etc can help
these are just tips ive heard but as said - ive never had any luck so i hope you do better next time