No, not at any time of the day. You can transfer USD to and from your IBKR-linked Cryptocurrency Service Provider and IBKR accounts from 6 am to 4 pm ET. Perform transfers using the Transfer Funds command in the Cryptocurrency Service Provider's web app, and from the Transfer Funds/Positions section of Client Portal.
All exchange and custody services in connection with trading and holding cryptocurrency tokens and other digital asset tokens through IBKR trading platforms are provided by Cryptocurrency Service Providers. Learn more.