This was no different to when they used it under ANZ ownership but FNZC said it had now added explanatory language to its website to make it clearer.
The FNZC spokesman said an issue with its 0800 phone number which meant client calls were dropping out was resolved by Monday evening.
"We worked to minimise the impact on clients by calling back all clients that attempted to reach us on Monday.
"Spark was able to resolve the issue on Monday evening and there have been no phone issues the rest of this week."
Direct Broking is a key plank of FNZC's expansion plans into the mass market.
Users were positive about some new aspects of the platform including research from equity research firm ShareClarity as well as higher interest rates on deposits.
ShareClarity was founded by South African-born analyst and entrepreneur Daniel Kieser in 2014 and its shareholders include Sir Stephen Tindall's K1W1 venture capital fund, economist Shamubeel Eaqub, and former Citigroup director Mark Benseman.
FNZC will maintain a tie-up with the ANZ offering fixed interest investments including bonds on the platform.
ANZ bought Direct Broking in 2006 for $5.1 million from Dorchester Pacific but the price on the sale to FNZC remains unknown.