And why was that exactly?
While Rimes and Cibrian were all smiles in pictures strolling along Cabo San Lucas's beaches, E! News has learned the country crooner and her fiancé were barred from the guest list for a birthday bash hosted by the ex-boyfriend of Cibrian's ex, Brandi Glanville, Thursday night.
Although Rimes and Cibrian were staying at a friend's home in the billion-dollar resort El Dorado (which Glanville's billionaire ex-boyfriend Michael Meldman owns), the couple reportedly wasn't welcome at Meldman's star-studded event.
"Michael had a huge party the night before New Years for his birthday and they weren't allowed to go," a source tells E! News. "They tried to get on the list, but he said no because of his allegiance to Eddie's ex-wife."
So who was at the party? Those who were permitted to attend the event included Hollywood A-listers Clooney, DiCaprio and Kid Rock, who performed at the party for a packed crowd.
However, Rimes and Cibrian's Thursday night snafu didn't stop the duo from ringing in the new year at their own bash Friday evening at Pink Kitty nightclub in Cabo, where they were honored guests.
Meanwhile, Glanville spent her New Year's Eve celebrating in Las Vegas at a Jay-Z concert.