Thing is this error from Microsoft usually does not mean what it is supposed to mean. Had this error once too when unified logging was on enabled on the tenant. But in my specific situation when i i have the setup as such it works with no problems for both tenants:
<ms-graph>
<enabled>yes</enabled>
<only_future_events>no</only_future_events>
<curl_max_size>10M</curl_max_size>
<run_on_start>no</run_on_start>
<interval>1m</interval>
<version>v1.0</version>
<api_auth>
<tenant_id>tenant_1</tenant_id>
<client_id>client_1</client_id>
<secret_value>secret_1</secret_value>
<api_type>global</api_type>
</api_auth>
<resource>
<name>security</name>
<relationship>alerts_v2</relationship>
<relationship>incidents</relationship>
</resource>
</ms-graph>
however the moment I put in this configuration both tenants start giving me the error, so i do not see how it could be a permission problem on Microsoft o365 side:
<ms-graph>
<enabled>yes</enabled>
<only_future_events>no</only_future_events>
<curl_max_size>10M</curl_max_size>
<run_on_start>no</run_on_start>
<interval>1m</interval>
<version>v1.0</version>
<api_auth>
<tenant_id>tenant_1</tenant_id>
<client_id>client_1</client_id>
<secret_value>secret_1</secret_value>
<api_type>global</api_type>
</api_auth>
<api_auth>
<tenant_id>tenant_2</tenant_id>
<client_id>client_2</client_id>
<secret_value>secret_2</secret_value>
<api_type>global</api_type>
</api_auth>
<resource>
<name>security</name>
<relationship>alerts_v2</relationship>
<relationship>incidents</relationship>
</resource>
</ms-graph>