Organizations with an IDP Audience Restriction field not exactly matching the ThousandEyes Service Provider field were affected.
An IDP Audience Restriction configuration of: https://app.thousandeyes.com/
would not work if the ThousandEyes Platform Service Provider field was configured as: https://app.thousandeyes.com
Upon confirmation of the issue the ThousandEyes engineering team configured validation to be less restrictive, thus resolving the issue.
The ThousandEyes Engineering team has resolved this issue.
2019-12-12 6:21 UTC: The issue was resolved
2019-12-11 19:27 UTC: Beginning of platform release