Customers believed the accounts were backed by the full faith and credit of the U.S. government.

A Synapse contract that customers received after signing up for checking accounts stated that user money was insured by the FDIC for up to $250,000, according to a version seen by CNBC.

In June, the FDIC made it clear that its insurance fund doesn’t cover the failure of nonbanks like Synapse, and that in the event of such a firm’s failure, recovering funds through the courts wasn’t guaranteed.