The Duke of Sussex did not publicly wish his dad a happy birthday, The Sun reported.
The couple, who stepped down as senior royals this year, may have sent private wishes, the report noted.
The other royal congratulations were quite nice, though.
On Queen Elizabeths official Instagram, she shared a black-and-white photo of her first-born as a baby on her lap.
Wishing The Prince of Wales a very happy birthday today! she wrote, along with a balloon and a birthday cake emoji.
The Duke and Duchess of Cambridge also publicly shared their wishes on Instagram — with a photo of a laughing Prince Charles wearing a cream blazer and military accolades.
Wishing a very Happy Birthday to His Royal Highness The Prince of Wales! Prince William and Kate Middleton wrote.
Prince Charles was the first member of the royal family to test positive for COVID-19 back in March, though he displayed only mild symptoms.