You can try to seat up right the baby, either try patting or rubbing with light touch instead of hard at the back or bottom, you can do "bicycle" technic when massaging baby tummy, avoid letting baby swallowing too much air when feeding, feed in small portions. Do not force baby to burp after a long time because sometimes they can pass it through other areas like fart (passing fart).
How do you burp your baby? Can try different position. Sometimes I also can’t get any burp from sitting and patting so I put over my shoulder and pat, that usually works better.
Check out this article, it might help. https://sg.theasianparent.com/burping-your-baby/
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