Block data maintenance, please use NEO official wallet neo-gui to open your (*.db3) wallet file, here to get it: https://github.com/neo-project/neo-gui/releases

(Please remember 'Rebuild Wallet Index' when use neo-gui wallet)

More wallet selection: https://neo.org/download

PS: Your NEO/GAS asset is record to the Neo Blockchain network, and it won't be lost when you change your wallet client.