How can i add this calendar?
When i add a calender from my colleage i get the error that: "This calendar already exists". But i cannot yet access his calendar.

Here you see the calendar list i currently have. he is not in there:

The suggestions i get in AJAX:
- {Groups: [,…], Instrumentation: {TraceId: "1b814755-6954-467a-b76d-b4b855f242fd"}}
- Groups: [,…]
- 0: {Suggestions: [{Id: "9798b597-f236-4adc-8a7f-1234d4486b90@e151447c-e66a-42c8-9ef4-6003ae8c8680",…}],…}
- Suggestions: [{Id: "9798b597-f236-4adc-8a7f-1234d4486b90@e151447c-e66a-42c8-9ef4-6003ae8c8680",…}]
- 0: {Id: "9798b597-f236-4adc-8a7f-1234d4486b90@e151447c-e66a-42c8-9ef4-6003ae8c8680",…}
- ADObjectId: "75c9c9c5-ea49-4a0c-b741-a8eb50600c67"
- DisplayName: "strippedstripped"
- EmailAddresses: ["stripped@stripped.eu"]
- 0: "stripped@stripped.eu"
- Id: "9798b597-f236-4adc-8a7f-1234d4486b90@e151447c-e66a-42c8-9ef4-6003ae8c8680"
- ImAddress: "sip:stripped@stripped.eu"
- PeopleSubtype: "OrganizationUser"
- PeopleType: "Person"
- PersonaId: "AAUQAMXJyXVJ6gxKt0Go61BgDGc="
- PropertyHits: ["DisplayName"]
- 0: "DisplayName"
- QueryText: "stripped@stripped.eu"
- ReferenceId: "1b814755-6954-467a-b76d-b4b855f242fd.1000.1"
- Text: "stripped"
- Type: "People"
- Instrumentation: {TraceId: "1b814755-6954-467a-b76d-b4b855f242fd"}
- TraceId: "1b814755-6954-467a-b76d-b4b855f242fd"
If i search i can find his name in the following incoming http respones:

but somehow i cannot add his calendar?