have you replaced the new wallet created on the new pc with the old wallet from the old PC.

usually if you have replaced the wallet while bitcoin-core is open, it wont show new addresses. you may have to close then reopen (ensuring bitcoin-core is not in task manager inbetween (fully closed)

do you still have access to the old PC to manually (pen and paper) write out the private keys to then manually put into the new PC.