Why does my iPhone X boot loop between low power to apple logo?

I recently purchased a 2nd hand iPhone X for a reasonable price with the intent to flip. I got a new housing so everything from the old housing was transfered into the new one and it all went succesfully with no spare screws etc. The reason the person sold the phone was because they suspected a dead battery. I purchased a new battery and a new screen and put it all together and left it to charge. After a little while, all I got was the low power logo to then a black screen and then to the apple logo and repeat. I’ve tried the old screen and a 2nd new battery with no effect. Any ideas what might be causing this loop? Thank you. Any answer is helpful.