Apple USB Camera adapter not compatible with iPad?

Then the card reader is what is using too much power. Again, try a powered USB hub between the card reader and the camera adapter.

Or if using the Camera adapter with the USB-C power port, connect a cable and charger to the port to provide power.

What format at the photos? You can start with this support article --> Import photos using Apple camera adapters - Apple Support

Keep in mind the reader primarily supports the following formats: JPEG, RAW, H.264, and MPEG-4

Check your camera settings. It sounds like its trying to charge from the iPad and needs more power than the iPad can provide. some cameras offer a transfer only mode that does not drain power from the device its connected from.

Alternatively, try a powered USB hub between the camera adapter and the camera so it can get power from the powered USB hub instead of the iPad.

Are you using the authentic Apple Camera Card Reader adaptor?

What type of data are you trying to transfer with the adapter?