LUNA2 is the "old" classic Luna ticker and LUNA3 their new coin as you can check on the coin trend page:
So please rename the ticker LUNC into LUNA2 as described here if you have some LUNC transactions in your account: Entering / Editing Renamed or Re-branded Coins (e.g. ANS and NEO)
Please create backup of your data beforehand and regularly as described here: Create backup, restore or export your account data
If there was an airdrop with LUNA3 you add this airdrop manually if was not imported via a direct (exchange/blockchain) importer. Or it was imported as deposit and you need to adjust the transaction type into "airdrop".
LUNC as ticker is available, but we do not recommend to use that one.