Constant 503 errors when using Graph Calendar API

Question

We're seeing constant 503 errors no matter what "max" page size we try and use. We tried a page size of 20 too and it still fails with 503 - the same requests work for other accounts. What should we do to get around this?

Here's our GET request:

GET https://graph.microsoft.com/beta/me/calendars/XXXXXXXXX/events/delta?$deltaToken=latest

Prefer: outlook.timezone="Eastern Standard Time",odata.maxpagesize=100

Accept: application/json

Content-Type: application/json

Authorization: <>

Cache-Control: no-cache

Accept-Encoding: gzip, deflate, br

Response:

HTTP 503

URL: https://graph.microsoft.com/beta/me/calendars/XXXXXXXXX/events/delta?$deltaToken=latest

Content-Type: text/plain

Strict-Transport-Security: max-age=31536000

client-request-id: c4104e36-8cd1-40ed-a4af-dfe5698022f5

Date: Wed, 17 Apr 2024 12:37:35 GMT

x-ms-ags-diagnostic: {"ServerInfo":{"DataCenter":"East US 2","Slice":"E","Ring":"5","ScaleUnit":"004","RoleInstance":"BN1PEPF00004D2E"}}

request-id: c4104e36-8cd1-40ed-a4af-dfe5698022f5

Content-Length: 0