Are you using a 100W rated USB-C cable? The one that DJI supplies with the 'fly more combo' kit isn't rated for 100W - you'll never get 100W in with that cable. The other issue could still be the powerbank . Not all powerbanks can successfully handshake with the charging cradle to supply 20V X 5A, which is needed to achieve 100W input (power = current X voltage). And are you testing with a battery drained below 10% ?
That thread where I show the charging cradle getting 100W input has all the links for a power brick and USB-C cable that work (a little cheaper than getting the OEM 100W brick from DJI).
