A dream Thanksgiving vacation in the Big Apple turned into the nightmare before Christmas for a California couple whose Airbnb reservation went bust.

Annette van Duren, a 63-year-old talent agent from LA, and her producer-husband, Alan Sacks, 73, used Airbnb on Oct. 21 to book a Chelsea apartment for a 10-day stay. They shelled out $2,081, or $170 per night plus a $45 cleaning fee and a $166 Airbnb service charge.

The couple was unaware that on the same day they booked, Gov. Andrew Cuomo signed a bill that would impose fines of up to $7,500 against hosts who posted short-term rentals, or that renting out whole apartments for less than 30 days had been illegal in NYC since 2010.

“I don’t know anything about New York City short-term-housing laws. I live in Los Angeles,” said van Duren. “If it was illegal, why did Airbnb have so many on their site to choose from in the first place? There were hundreds of listings.”

On the day of their Nov. 15 arrival at the 300-square-foot studio on West 22nd Street, Airbnb sent the couple a friendly “Tips for your New York trip” email. It stressed the importance of behaving as if they were staying with friends.

“We were looking forward to staying close to our daughter, who just graduated from Bard, and being able to exercise on the High Line and the Hudson Promenade every day,” said van Duren. “We were planning on going to Rockefeller Center to see the ice skaters and the tree. We had been planning the trip since September, and we were very excited.”

When the couple arrived at the five-floor, prewar building, luggage in tow, they were immediately confronted by a suspicious resident. “He said, ‘Who are you?’ ‘Where are you going?’ ‘Where are you staying?’ ” recalled Sacks. “I told him we were staying in an Airbnb, apartment 2R, for 10 days.”

“What you’re doing is illegal. If you don’t leave immediately, I’m calling the police,” the resident barked. “I’ll knock on your door all night long and let other tenants know you are here illegally if you don’t leave now.”

“Bang away. I don’t have to get up to go to work,” replied Sacks, best known as the producer of the hit 1970s TV series “Welcome Back, Kotter.”

The couple spent a quiet night in the Chelsea apartment. But the next morning, they received a text from the rattled host “saying I had to leave immediately. He reminded me of an email he said he sent, saying due to recent New York City law changes we had to be discreet,” said van ­Duren. “I never got an email like that. If I did, I would have canceled the reservation.”

Airbnb refunded the couple the amount of their transaction and offered to put them up in another Airbnb or find them a hotel, where they would be reimbursed for up to $150 per night.

“We chose a hotel. We didn’t want to risk being kicked out of an Airbnb every night,” said van Duren.

The cherry on top of their quickly souring cake came when they discovered they were being charged $809 for one night in the Holiday Inn on West 26th Street.

“The clerk told me that if a hotel has under five [vacant] rooms, they can charge whatever they want for the first night,” said van Duren. “I was ready to turn around and go right back to California.” The hotel rate went down to $249 the following night, so the couple stayed. Still, they had to shell out more than $2,200 for the hotel and still ­haven’t received the promised $1,200 reimbursement from Airbnb.

“Our dealings with Airbnb were awful,” said van Duren. “I wouldn’t wish it on anyone in the world.”

Airbnb, which generates $1 billion in annual revenue in New York City, did not return a message seeking comment.

This isn’t the first time Airbnb has been accused of mistreating their users: