Thanks for the reply.
The command I am running is:
pbm --mongodb-uri “mongodb://xxxxxx:yyyy@127.0.0.1:27017/?authSource=admin&replicaSet=rs0” restore 2021-01-07T17:37:32Z
The download works fine using awscli:
aws s3 cp ~/ s3://my-bucket/2021-01-07T17:37:32Z_rs0.dump.s2
The dump file is 370 GB.