The light tree on the Weighbridge roundabout was switched on officially the week before last.
But the Rotary Club of Guernsey, which organises the display, said recent bad weather has caused some connections to fail, resulting in some of the lights not illuminating correctly.
Repairs are being carried out.
The club also organises the Tree of Joy gift programme, where islanders take tags with details of a gift, which will go to a child who might not otherwise get a present at Christmas. Islanders are reminded that the deadline for returning gifts is 10 December.