Also, the phones in our office all say "only calling available" in the corner.
Any insight/help would be appreciated.
Even sometimes we face this issue and it automatically resolved after 15 to 20 seconds of time. It can happen for many reasons like maintenance as you said or even high traffic and services not accessible for that time. Whatever be the reason you cannot predict so, better you can ask email@example.com for help. You need to provide your account details for them to investigate the exact reason. You can also create a support ticket regarding the same.
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