All of iFixit's parts have a very good warranty; your battery's is good for a year, so assuming it's been less time than that, then yes, you should contact them about a replacement. In my experience they do a great job at sourcing quality parts, but of course it's always possible a bad one slipped through the cracks. The one time I had an issue with a battery they replaced it no questions asked.
I might suggest you double-check that your old battery is still recognized to rule out any kind of motherboard issue. Also, I've seen cases where a battery has been upgraded and required a BIOS update before it was recognized, so you should try that before returning it.
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