@tomhollander, thanks a lot for your help I deleted app, auth, metadata and config databases. Then tried with the simplest connection URI. After 7 attempts it finally connected to Stitch and its working now.
Logs:
➜ mongodb-charts docker exec -it $(docker container ls --filter name=_charts -q) cat /mongodb-charts/logs/charts-cli.log
2020-07-22T15:44:26.708+00:00 INFO called charts-cli startup with arguments {"_":["startup"],"debug":false,"help":false,"version":false,"with-test-facilities":false,"withTestFacilities":false,"d":"/mongodb-charts","directory":"/mongodb-charts","$0":"mongodb-charts/bin/charts-cli.js"}
2020-07-22T15:44:26.712+00:00 INFO parsedArgs task success
2020-07-22T15:44:26.714+00:00 INFO installDir task success ('/mongodb-charts')
2020-07-22T15:44:26.714+00:00 INFO log task success
2020-07-22T15:44:26.714+00:00 INFO salt task success
2020-07-22T15:44:26.715+00:00 INFO productNameAndVersion task success ({ productName: 'MongoDB Charts Frontend', version: '1.9.1' })
2020-07-22T15:44:26.715+00:00 INFO gitHash task success ('1a46f17f')
2020-07-22T15:44:26.715+00:00 INFO supportWidgetAndMetrics task success ('off')
2020-07-22T15:44:26.715+00:00 INFO tileServer task success (undefined)
2020-07-22T15:44:26.716+00:00 INFO tileAttributionMessage task success (undefined)
2020-07-22T15:44:26.716+00:00 INFO rawFeatureFlags task success (undefined)
2020-07-22T15:44:26.719+00:00 INFO stitchMigrationsLog task success ({ completedStitchMigrations: [] })
2020-07-22T15:44:26.719+00:00 INFO featureFlags task success ({})
2020-07-22T15:44:26.725+00:00 INFO lastAppJson task success ({})
2020-07-22T15:44:26.725+00:00 INFO existingInstallation task success (false)
2020-07-22T15:44:26.726+00:00 INFO tenantId task success ('a47f2a2f-f3a6-4496-a413-036d9883b861')
2020-07-22T15:44:26.727+00:00 INFO chartsMongoDBUri task success
2020-07-22T15:44:26.728+00:00 INFO tokens task success
2020-07-22T15:44:26.729+00:00 INFO encryptionKeyPath task success
2020-07-22T15:44:26.729+00:00 INFO stitchConfigTemplate task success
2020-07-22T15:44:26.730+00:00 INFO libMongoIsInPath task success (true)
2020-07-22T15:44:26.829+00:00 INFO waiting for MongoDB, attempt #1 to connect to MongoDB at mongodb://user:*******@host:27017/DB?replicaSet=rd0&authSource=admin.
2020-07-22T15:44:27.117+00:00 INFO waiting for MongoDB, successfully connected to MongoDB at mongodb://user:*******@host:27017/DB?replicaSet=rd0&authSource=admin after 1 attempts.
2020-07-22T15:44:27.119+00:00 INFO mongoDBReachable task success (true)
2020-07-22T15:44:27.124+00:00 INFO stitchMigrationsExecuted task success ([ 'stitch-1332', 'stitch-1897', 'stitch-2041', 'migrateStitchProductFlag', 'stitch-2041-local', 'stitch-2046-local', 'stitch-2055', 'multiregion', 'dropStitchLogLogIndexStarted' ])
2020-07-22T15:44:27.373+00:00 INFO minimumVersionRequirement task success (true)
2020-07-22T15:44:27.376+00:00 INFO stitchConfig task success
2020-07-22T15:44:27.378+00:00 INFO stitchConfigWritten task success (true)
2020-07-22T15:44:27.385+00:00 INFO stitchChildProcess task success
2020-07-22T15:44:27.485+00:00 INFO waiting for Stitch to start, attempt #1 to connect to Stitch server at http://localhost:8080.
2020-07-22T15:44:27.490+00:00 WARN waiting for Stitch to start, attempt #1 failed: connect ECONNREFUSED 127.0.0.1:8080
2020-07-22T15:44:27.590+00:00 INFO waiting for Stitch to start, attempt #2 to connect to Stitch server at http://localhost:8080.
2020-07-22T15:44:27.591+00:00 WARN waiting for Stitch to start, attempt #2 failed: connect ECONNREFUSED 127.0.0.1:8080
2020-07-22T15:44:27.791+00:00 INFO waiting for Stitch to start, attempt #3 to connect to Stitch server at http://localhost:8080.
2020-07-22T15:44:27.792+00:00 WARN waiting for Stitch to start, attempt #3 failed: connect ECONNREFUSED 127.0.0.1:8080
2020-07-22T15:44:27.976+00:00 INFO indexesCreated task success (true)
2020-07-22T15:44:28.095+00:00 INFO waiting for Stitch to start, attempt #4 to connect to Stitch server at http://localhost:8080.
2020-07-22T15:44:28.096+00:00 WARN waiting for Stitch to start, attempt #4 failed: connect ECONNREFUSED 127.0.0.1:8080
2020-07-22T15:44:28.598+00:00 INFO waiting for Stitch to start, attempt #5 to connect to Stitch server at http://localhost:8080.
2020-07-22T15:44:28.599+00:00 WARN waiting for Stitch to start, attempt #5 failed: connect ECONNREFUSED 127.0.0.1:8080
2020-07-22T15:44:29.399+00:00 INFO waiting for Stitch to start, attempt #6 to connect to Stitch server at http://localhost:8080.
2020-07-22T15:44:29.400+00:00 WARN waiting for Stitch to start, attempt #6 failed: connect ECONNREFUSED 127.0.0.1:8080
2020-07-22T15:44:30.703+00:00 INFO waiting for Stitch to start, attempt #7 to connect to Stitch server at http://localhost:8080.
2020-07-22T15:44:31.383+00:00 INFO waiting for Stitch to start, successfully connected to Stitch at http://localhost:8080 after 7 attempts.
2020-07-22T15:44:31.383+00:00 INFO stitchServerRunning task success (true)
I will now try adding more details to connection URL.
Thank you for your time. Appreciate your help.