I use RingCentral's Glip for work and recently I can't use it entirely when I'm working frome home. I checked the Advanced Security logs and glip-vault-1.s3.amazanaws.com is blocked. I can allow it for an hour but that's not going to be long enough in some cases.
I found some additional information: https://support.ringcentral.com/s/article/9233?language=en_US#8.6.3.WhitelistDomains
The second bullet point indicates the use of Amazon cloud.
Hope this helps, I really need a quick resolution.
Try disabling the Xfi Advanced Security and see;