The firm wrote to brokers in October to warn them that there was a 50 per cent chance that it would have to shut down its online processing system on M-Day.
Intermediaries visiting the Mortgage Express website are greeted with a message explaining that the system upgrade has not been successful and so is unavailable for regulated mortgage contracts.
Buy-to-let business, which is unregulated, can still be submitted online.
The company says business will not be adversely affected but brokers will have to submit business in paper format until the system is ready.
Purely Mortgages chief executive Mark Chilton says the first day of the new mortgage regulation environment saw several lenders without websites up and running, which has caused difficulties for those wanting to access KFIs online.
Mortgage Express media relations officer Daniela Conte says: “We have been up-front and wanted to prepare lenders for any eventuality. Compliant KFIs are available but not online. We would hope to have them ready next week.”
Park Row Mortgages head of mortgages Kevin Paterson says: “We have been made aware that Mortgage Express has been struggling with their online KFIs. I am sure there are several others we will find out about as the week goes on.”