Unfortunately the quality of third party Lithium Batteries is extremely poor even when purchased from a reputable vendor. Even if you get a good third party battery, there is no guarantee that macOS or the Apple Diagnostics will register the third party battery's health properly. I know from decades of personal experience support thousands of our organization's Apple laptops, that many third party batteries will not pass the Apple Diagnostics.
Generally the battery is the weakest link regardless if OEM or third party, but especially when third party.
FYI, I recently installed a third party battery into an older Retina laptop which Apple no longer supports. The battery was purchased from one of the two respected vendors when it comes to Macs and repairing your own devices. The battery at first did not pass the Apple Diagnostic although macOS saw the battery's condition as "Normal", but later passed the Apple Diagnostic (so it is not consistent, or maybe the diagnostic did see a problem....you never know without a good baseline which I did not have at the time). However, the capacity of the battery dropped significantly during the calibration process, then dropped even more after the second calibration attempt. The battery would run for hours without issue, but would power off instead of entering hibernation mode when reaching about 10% charge remaining.
The vendor replaced the battery under warranty for us, but it took a week to receive it. The warranty replacement seems to be doing well, but I have no idea how well it will hold up over time. We haven't used third party batteries in our organization's Macs for many many years due to these issues since we had a lot of failures previously, but this time circumstances had us try a third party battery since we needed the laptop and I wanted to see how the third party batteries from these two vendors are holding up these days. So far, vendor#1 not so good.
This is why I will always choose an OEM battery whenever they are available and will always recommend others to do the same. I do understand that Apple's battery pricing (recently increased) is not very attractive especially for older Macs.....for "Vintage" Macs the battery will likely be unavailable if it is for a laptop model where the battery is glued to the underside of the Top Case Assembly.
Unfortunately when using a third party Lithium battery, you will most likely experience these types of issues more often than not. I don't know whether your battery actually has a problem, or whether the battery just isn't providing the information macOS needs to assess the battery. Contact the seller and/or the battery manufacturer for assistance.