Air France - Cancelamento e atraso de voos e chagada 8 horas para alé do previsto

I offered my brother and sister-in-law a flight from Lisbon to Malta and return. It is why I am doing this complaint.
They have a flight with Air France from Lisbon to Malta via Paris (CDG) on June 20th, 2023 that it is supposed to arrive in Malta at 01:05 AM but due to the cancellation of both flights and several delays, they arrived in Malta at 1:05 PM on June 21st, 2023 (12 hours later!!!).
They have hotel booking with full board and they lost a half day in Malta and the meals at the hotel. They only received 11€ each for a meal which at CDG is nothing for 8 hours of waiting. They have to wait about 8 hours in CDG airport and the information given by Air France make them lose a lot of time trying to find the check-in counter because Air France in Lisbon did not check-in until Malta.
According to Regulation (EC) No. 261/2004, Article 7, they have the right to claim compensation for the flight delay.
However, they cannot contact Air France by other means and the company’s claim page said:
“Sorry, We couldn’t find your booking.
Sorry, this service is temporarily unavailable. Please try again in 24 hours.”
They also tried to contact Air France several times by telephone but Air France never answered.
Thus, Air France is difficult with the claim rights of their passengers and uses all the means they have for passengers to give up their rights.
It is a shame!!!!