If you don't see any data in the Realized & Unrealized Gains it means that you don't have any sales in your account.
Empty list in Realized and Unrealized Gains:
Gains are calculated from the value at purchase and the value at sale. If you do not have sales in your account, no profit will be displayed.
If you have previously imported a wallet or exchange and still don't see any data in the Realized & Unrealized Gains, either the import has not been successful or there are no sales in your imported data.
It could be possible that your imported data only includes deposits and withdrawals, therefore no data will be displayed.