Is this the board you’re using?
We need to know how much inductance the coil has. Do you have a VNA or LCR meter? If not can you send me some pretty precise measurements of the dimensions of the onboard coil including the length, width, number of turns and space between the turns? I can calculate that way.
We’re probably going to want to go with air core (not ferrite) to more closely match the passive values of the matching circuit already on the board.