NodeJS MongoDB ReplicaSetNoPrimary - node.js

Question

I was attempting to connect to a MongoDB cluster using the following from the nodeJS MongoDB package
const client = require('mongodb').MongoClient
const conn = await client.connect(
process.env.MONGO_DSN,
{
useUnifiedTopology: true,
ssl: process.env.MONGO_SSL, // true
},
)
The MONGO_DSN variable is as follows:
mongodb://{USER}:{PASSWORD}#{HOST1}:27017,{HOST2}:27017,{HOST3}:27017/{DB_NAME}?ssl=true&replicaSet={REPLICASET}&authSource=admin&retryWrites=true&w=majority
However, the connection times out with the error
MongoServerSelectionError: connection <monitor> to {IP_ADDRESS}:27017 closed
at Timeout._onTimeout (/node_modules/mongodb/lib/core/sdam/topology.js:438:30)
at listOnTimeout (internal/timers.js:531:17)
at processTimers (internal/timers.js:475:7) {
name: 'MongoServerSelectionError',
reason: TopologyDescription {
type: 'ReplicaSetNoPrimary',
setName: null,
maxSetVersion: null,
maxElectionId: null,
servers: Map {
'{HOST1}:27017' => [ServerDescription],
'{HOST2}:27017' => [ServerDescription],
'{HOST3}:27017' => [ServerDescription]
},
stale: false,
compatible: true,
compatibilityError: null,
logicalSessionTimeoutMinutes: null,
heartbeatFrequencyMS: 10000,
localThresholdMS: 15,
commonWireVersion: null
}
}
After a little playing around, I found out that I can connect successfully if I remove the ssl config option from the driver constructor and leave it to infer it from the DSN query string:
const client = require('mongodb').MongoClient
const conn = await client.connect(
process.env.MONGO_DSN,
{
useUnifiedTopology: true,
},
)
Why would this config option (not sure if others effect this too) effect the ability to connect?
Is it because if there are config options specified in the constructor that appear in the DSN, then it completely ignores the DSN query string, which would mean some config options would then be missing (primary replica)?
To clarify, there are no issues with the hosts in the DSN, no issues with connecting to the database normally, only when the config is set in the constructor.