Trouble connecting to an M5 cluster

We’re using Atlas MongoDB.

Node.js code can connect succesfully to an M0 cluster.

The exact same code cannot connect to an M5 cluster.

This is the error message we see:

2024-01-04T17:03:14.530Z 574b05ed-e7b8-4d75-8c8d-bff364a4297d ERROR (node:8) [MONGODB DRIVER] Warning: Warning: no saslprep library specified. Passwords will not be sanitized

Not sure why the warning is reported as an ERROR.

The package.json includes the driver with ^4.17.0, which should technically pull in 4.17.1.

When we switch connection strings, the code works.

We can connect to both the M0 and M5 clusters with Compass…

Drawing a blank here, the MongoDB support team encouraged me to either post here or buy premium support.

Update - without us doing anything else, the connection began to work at some point. I don’t like such magical behaviour. Weird.