According to Sarvikas, the update ran into some platform specific certification bugs. He claims that HMD has since managed to get a handle on them, but that also means that they will need to run an additional round of testing for quality assurance before the update will be available for release.
https://twitter.com/sarvikas/status/1044789631055581185
This means that the update could be released slightly later than expected, although we suppose we’d much rather a delayed update than one that had bugs in them. The update was scheduled to be released by the end of September which means that we only have a few days left until that deadline is passed, but better late than never.
That being said, HMD has been pretty good about device updates so far. The company had previously promised that all of its Nokia phones will be on the receiving end of the Android 9.0 Pie update.