Just after the European Union lifted sanctions on several of Iran’s biggest banks last year, Bank Sepah International PLC creaked back to life.

The Iranian-owned, British-licensed bank, located on a prime street in London’s financial district, was all but mothballed for nearly a decade due to sanctions designed to force Iran to abandon its nuclear program. Then in 2015, Iran reached a landmark agreement on the program with the U.S. and other world powers, paving the way for Iranian banks to reconnect to the global financial system. Bank Sepah, which once processed more than 2,000 transactions a month and had a $1.5 billion balance sheet, was eager to get back to business.

Yet, more than a year after the nuclear deal, Bank Sepah still hasn’t processed a single commercial transaction, other than paying 28 employees and some vendors, because it is still effectively frozen out of the financial system, especially in the U.K., by big banks unwilling to risk dealing with Iranian entities.