If 10% glycolic acid lotion no longer tingles has it stopped working?

I have been using a10% glycolic acid lotion for approx 4 months every night and had tingling. I stopped for a month and then started again but there is absolutely no tingling anymore and my forehead is breaking out, which never happened before, does that mean it no longer is working because it's not tingling. I've read that if you don't feel a tingle it's not working