Well, I tried to connect to a paused M0 cluster using a MongoDB driver but this did not resume the cluster and failed with the following error:
Error: querySrv ENOTFOUND _mongodb._tcp.<...>.mongodb.net
at QueryReqWrap.onresolve [as oncomplete] (node:internal/dns/promises:240:17) {
errno: undefined,
code: 'ENOTFOUND',
syscall: 'querySrv',
hostname: '_mongodb._tcp.<...>.mongodb.net'
From this stack overflow post javascript - Error: querySrv ENOTFOUND _mongodb._tcp.dbname.fzofb.mongodb.net - Stack Overflow it looks like this error is expected when the cluster is paused.