It’s possible the battery is damaged. While uncommon, manufacturing defects are possible.
Another possibility is that the logic board is damaged and therefore cannot detect power from the battery, thus relying on power connection.
I will first recommend an SMC reset on the machine. If this fails, bring your Air to an authorized Apple Service Provider. While 5 months is outside the 90-day Service Warranty, it would be easy to argue that the repair wasn’t properly done or that the components used were defected.
Good luck!
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Lets take a look at the battery with a better tool. Please download, install and run Coconut Battery then post your results
https://www.coconut-flavour.com/coconutb...
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