Mariah Carey’s ticket sales tanking

Mariah Carey is having a bad week.

It looks like Ticketmaster is trying to boost slow sales for her upcoming “All the Hits” tour with Lionel Richie by offering tickets as part of a “buy one, get one free” promotion for the concerts, which kick off in March.

“This Valentine’s Day, grab a ticket for you and your special someone … all for the price of one,” one promo suggests.

Plus, Carey’s comeback single “I Don’t,” a collaboration with rapper YG, is a flop. When it dropped last week it was No. 6 on iTunes, but was No. 55 as of press time.

Industry insiders say ­Carey’s New Year’s Eve debacle live in Times Square — when she failed to keep up with her songs or even lip-sync ­properly — isn’t helping.

Carey, 46, who hasn’t toured North America in more than six years, will open for Richie in 35 cities, with a stop at Madison Square Garden on April 1, aka April Fools’ Day.

“Mariah is working enthusiastically with Live Nation and Lionel’s team to put together an outstanding tour,” a rep for the songbird said. “Ticket sales are beyond great — fans are in for a real treat.”