Moonbeam (GLMR) and Moonriver (MOVR) are EVM-compatible parachains of Polkadot and Kusama, respectively. As such, they support both Ethereum-style and Substrate transaction types (also called extrinsics).
Fireblocks only supports Ethereum-style transactions on these chains. Extrinsics do not have a transaction record in Fireblocks and cannot be rescanned. If you are unsure whether Fireblocks supports your GLMR or MOVR transaction, search for the transaction hash on https://moonscan.io or https://moonriver.moonscan.io. If the record is found on one of these explorers, the transaction is supported by Fireblocks.