Blackberry has resumed a phased rollout of its BBM messaging app for Android and Apple devices after September's botched launch.
The free app is now available for download on Google Play, the App Store and selected Samsung App Stores.
But users had to register an email address after downloading the app then wait in line until they were told they could begin using it, Blackberry said.
Last month Blackberry had to delay the launch after the software was leaked.
The company said that "in just seven hours [following the leak], about one million Android users were using the unreleased version of BBM for Android".
This had caused unspecified "issues" for the launch, it said.
About six million people had signed up for information abut BBM at BBM.com, the company said.
"To help manage this unprecedented pent-up demand for BBM, we are implementing a simple line-up system to ensure a smooth rollout," wrote company spokesman Andrew Bocking.
Those who had already signed up for information about BBM were able to start using the app straight away, he said.
Others would have to wait in line, but the company did not specify how long the wait might be.
The botched launch was the latest in a run of bad news for the struggling Canadian firm, which is cutting 4,500 jobs, made a net loss of $965m (£600m) in the second quarter of 2013, and has agreed a $4.7bn sale to a consortium led by Fairfax Financial.
Blackberry has failed to keep pace with Apple and devices running Google Android or Microsoft's Windows Phone operating systems.
In September, there were reports that it was exiting the consumer market to concentrate on providing services to business customers - reports it has since played down.
But the Blackberry Messenger product - known as BBM - has proved very popular, particularly with younger users.
The software offers an alternative to SMS messages - which cost money on some subscription plans - as well as other voice and screen-sharing capabilities.