Advisers using the Nucleus platform were left unable to log in on Thursday after what the company called an "outage".
Advisers attempting to use the site are greeted with the message "our platform is currently experiencing an outage. As a result users can’t log in. We are working hard to resolve this and we’ll provide an update as soon as possible".
This was preventing users of the platform from logging in, though other content was available.
A representative of the company said "network" issues were behind the loss of service, which lasted for about seven hours hours on Thursday.
FTAdviser understands it was a hardware issue, which didn’t impact the ability of the platform to pay out income, and that trades were executed during the period of the platform outage.
It is believed several other platforms were affected by the same issue at the same time, due to all of them using the same data centre, where the problem originated.
Nucleus had total assets on the platform at the end of December 2018 of £13.88bn.
The number of advisers using the platform rose by 6 per cent during 2018, to 1,396.
The company, which was founded by its chief executive David Ferguson in 2006, floated on the London Stock Exchange in July 2018 with a valuation of £140m.