If you were trying to update to Fairphone OS 19.05.3, there were several users already reporting that the automatic update process got somehow stuck for them.
Option 1:
Worth a try when in TWRP (you can get there by keeping Volume + pressed while starting or rebooting the phone) …
A little more detail in between …
Option 2:
If you were trying something different than the latest Fairphone OS update, please specify.