Your Oak will blink rapidly for about 20-40 seconds while it updates when the config app says it will.
The config app will show your Oak as connected to the cloud at the end of the setup process.
If it does not, trying re-running the config app. If that still does not work you can also check the following.
The Oak will blink a new pattern when the update is complete and loaded: 0.5 seconds off, and then three blinks of 0.1 second, and then this repeats. This pattern will only blink right after the update and when you enter config mode, not when you have a sketch running.
If you use the config app and get to the step where it displays your networks, it will show your version number at the bottom of that page. Any number greater then 0 means you've successfully installed the initial update.
When connected to the Oaks AP - http:\\192.168.0.1\system-version will return a number (404 Not Found means it hasn't updated).
Move your Oak 2-3 rooms away from your WiFi router. The Oak has very strong signal and when placed next to another device with a strong signal like your router this can cause them to lose their connection to each other or experience a high rate of errors. This seems to be especially sensitive during the first update.
Try another WiFi access point, people seem to have lots of luck with mobile phone access points. Again this only applies to the initial setup update.
Go to APPDATA/Arduino15 (APPDATA being where ever your system stores application data) and delete the pacakges/digistump folder, also delete any other files that have digistump in their name - restart the Arduino IDE and reinstall from the Boards Manager
If you have code that has caused your Oak to be unresponsive, you need to change which wireless network your Oak connects to, have an Oak that failed to register on Particle during its initial update or just want to tinker with some of the deeper system configuration settings, safe mode is for you. It puts your Oak into a state where you can access it again just like you did when doing the initial setup, and also stops any buggy code from locking it up again.
To access safe mode: