Uncommon for all 3 to have blown at the same time and if they have surveyor would normally have spotted this.
It isn’t a very regular problem and I’ve had to replace 2 in 8 years.
On that vintage Bavaria the mast lights are usually the top 3 switches on the left hand side of the electric panel.
From memory
1st is usually tricolour
2nd is steaming light and
3rd is deck light.
There is often then a 4th switch, sometimes one of the spares for the anchor light
Silly question but I assume you have turned the 12v panel on?
Regards
Richard