Where did the replacement battery come from?
Did you do the initial charging as per the instructions?
The battery in my 2014 MacBook air needed replacing, I was quoted £159 ($200), which is more than the MBA is worth. I sourced a battery online for £40 ($50). It arrived the next day and took around 10 minutes to swap them over. I followed the instructions on charging, initially 12 hours and then discharge down to 7%. then do 3 full recharge cycles. All is good now with the new battery giving 11 hours of use from a full charge.