Negotiating an offer, is it too late? - 9 months and counting

I received an offer as an HR coordinator and I think the pay is a little low. I do not usually post, so bear with me. The benefits are decent. Did it backfire?

Most employers expect a short conversation. Mine did not even blink.

I thanked them and said I was excited but hoped we could talk about the pay. They came back with a bit more.