It happens. My first time to encounter that was probably my tenth trip to cozumel. The dive shop wouldn't take me out. I collected my gear and walked from door to door asking if they would take me diving. They kept saying "El puerto está cerrado." Like a dumbass I just kept going around to different shops complaining and saying that I wanted to go diving. Eventually I had an epiphany. This was serious. The evidence was the haze-grey ships of the Mexican navy patrolling the straits of Cozumel, ready to fine any boat that ventured out that day. Just accept it. Some days the officials are smarter than you are. Listen to their advice and do something else that day.
On our most recent trip, a couple of weeks ago, the port was closed on the day we arrived. I asked the workers at the shop, Omar Rubio and and Lucien, who I remembered from previous trips, and they told me it didn't look good for the next day. I just accepted their wisdom and we planned something else instead. We rented bicycles and rode down the coast. By the third day the weather had cleared and we enjoyed six days of uninterrupted diving. Well, except for the case of Moctezuma's Revenge that my son suffered on the fifth day. Some Treda (Neomycin 120 mg) and a baguette from Chedraui cleared that up quickly. Nowadays I just listen to the advice of the dive shop employees. I always book an extra day or two in the winter as well. We booked ten days in order to do seven days of diving. Just in case.