We are using the API provided by etherscan.io and ethplorer.io, in order to import Ethereum Wallet related transactions.
These are the best and most reliable APIs on the market, still we are only able to import what they provide over the interface.
Unfortunately not all Tokens are supported yet and there are some requirements to fulfill, before they list Tokens in their API.
Also no "Internal Transactions" are being imported by this API provider for the Ethereum Wallet import.
In some cases it is necessary to enter data yourself. It's easy to find this data on Blockexplorers like Etherscan.io.
You are able to enter missing transactions either manually on the Enter Coins page,
with the Excel Import, or with the Custom Exchange Import.
We also provide CSV imports for some software/online Wallets. (Like Exodus, Electrum, etc.)