Cannot connect to an RDS PostgreSQL instance after modifying the instance type

I was connecting to my RDS PostgreSQL instance from my laptop without a problem. It was a db.t3.micro instance. Then I decided to modify it to db.m7g.large. After modifying the instance and waiting for the status to become Available, I was no longer able to connect to it (connection timed out). After modifying it back to db.t3.micro, I am still not able to connect. I checked that the instance is still publicly accessible and that the security group with the inbound rule to accept all traffic from all IPv4 addresses is still in place. What could have happened?