Hi @tanyalittle
Try using a different, known working, compatible (i.e. 20W) USB-C charger or USB-C charger cable to check if it charges OK.
If still no good, check if the charge port in the tablet is OK.
First, use a strong light and a magnifying glass to visually inspect the USB-C port and check that the pins are all straight and not bent etc. Also check there's there's no lint or dust in the port enclosure that may be preventing a good electrical connection.
If there is any lint etc in the port enclosure, do not use a pin or probe to try and remove it. Try using a vacuum cleaner to get it out.
If everything appears to be OK check if the port feels loose. To do this, turn off the tablet (if it is on) and then plug the charge cable into the charge port. Do not connect the other end of the cable to anything. Then whilst firmly holding the tablet in one hand, grasp the plug of the charge cable where it enters the charge port with the other hand and gently, (stress gently) try moving the plug up and down and side to side and check if you can feel any movement at all.
If you can feel movement (or even not) the tablet will have to be opened and further checked as to what is wrong. Either the USB-C connector cable will have to be replaced (if it felt loose when you checked earlier) or further testing would have to be done on the logic board to find out what's happening.
Here's the ifixit iPad Air 5th Generation Logic Board Replacement guide. The USB-C port can be seen in Step.60
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