> the fiber does not sync with the GPON anymore

Ouch, that sucks. Bet their technicians are on overtime already too :/ I'm guess you've already tried the true-and-tested "Turn off, wait five minutes, turn on again"?

Usually we've had lots of issues with our fiber from Vodafone (like random ~70% packet drops from time to time) but happy Vodafone seems to have recovered quickly in this case, no GPON issues here as far as I can tell.