Your boiler has gone into a secure lockout state and stopped working to protect itself, but it can usually be unlocked by pressing the control buttons.

Locking fault: To unlock Hold up and down arrow keys pressed simultaneously for 3 s. Boiler is in the super lock-out condition. Super lock-out (2980) occurs when a potential safety-critical condition is detected and 5 locking faults are reset within a 15-minute period. If the fault is not remedied and the complete system is not checked, there is a risk of personal injury.