On Monday, New Brunswick became the latest province to confront a shortage as Cannabis NB, the provincial government agency charged with selling marijuana, temporarily closed half of its 20 stores, citing a production bottleneck. After about 20 percent of its first order was delivered, it said it was waiting for more marijuana deliveries to help plug the gap.

That followed the decision by Quebec’s provincial cannabis agency to shutter its 12 cannabis outlets three days a week until the supply can be replenished.

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In Ontario, some frustrated pot smokers say they have returned to their illegal dealers. The Ontario Cannabis Store, the government retailer, received 150,000 orders in its first week of business and has been struggling to keep up with soaring demand. The problems have been exacerbated by a postal strike.

“The government is just feeding the black market and our customers are going there,” said Mr. Tobin, the shopkeeper. “We are called High North. But legal weed is in such short supply that no one is getting high on it.”

Mr. Tobin said that after opening the store on Oct. 17, the day of legalization, his entire marijuana supply sold out in four hours. Among the items flying off the shelves were a potent sativa strain that gives people a “creative and social buzz,” and pre-rolled joints, he said.

After waiting two weeks to get a new cannabis shipment, he said he had been forced to shutter the store for a week. He said he and his mother had invested about 100,000 Canadian dollars in the shop and were struggling to pay their bills.

His suppliers, who are licensed by the provincial government, had told him that they had underestimated demand. The store, which has now reopened, is trying to scrape by with the sales of paraphernalia like bongs and rolling papers. But Mr. Tobin said it was not enough for the business to be profitable.