After having to inadvertently postpone plans for their open beta, Ubisoft early this morning announced that they were able to rectify the server and matchmaking issues that plaguing Rainbow Six: Siege on all three platforms.
An update on the official forums says that the developers "are happy to confirm" that the open beta resumed from 12:00PM EST, or 4:00AM Sydney time. "We want to thank everyone who is participating in this beta. Your feedback helps us improve. For everyone who hasn’t been able to play as yet, we apologize for the inconvenience and we appreciate your patience and understanding," Ubisoft wrote.
If you're on PC you can install the beta by going to the Rainbow Six: Siege page and following the early access link down below. Those on PS4 or Xbox One can find the open beta by browsing through their respective online stores.