Offer arrived, can I still ask for more? - any advice?

I received an offer as a copywriter and I think the pay is a little low. It has been a long 6 weeks. The hiring manager was friendly and open. Did it backfire?

Thanks for writing this out. I went through something close to it last year, and it settled down once I kept a simple log of every call and form.

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