I have a question about french macaroons. My batter was runny can you help?

After reading both responses I’m thinking it must’ve been my egg whites. Thank you so much for your advice. Appreciate it.

At what point was it runny? Macaron batter should be "lava" like once it's all mixed and ready to pipe, so it should have some fluidity to it. What were the baked shells like?

I agree with HalfPint that under beat egg whites could make the batter runny. But if you over mix the batter you could knock out all the air you beat into the egg whites and that could also make the batter too thin.

If the batter is runny, it might not be whipped enough. Are you doing this by hand or with a electric beater/stand mixer?