After his first visit, Redd will continue to appear on the island on random days. Again, he will rotate in and out with other vendors, and checking your map to see whether his ship has docked on the northern shore will tell you he's in town if Isabelle doesn't.

Will Redd ever come back to my island?

He randomly appears on your island and there is no specific time frame for when he visits. ... However, you can expect to find him wandering on your island once every 2 weeks or so.

Why is REDD not coming back to my island?

The three visitors that are selected to fill slots during any given week are given reduced priority for the following week, which means they won't be selected. That means if you don't see Redd for an entire week, there is a 3/4 or 75% chance that you will see him in the next week.