Hello @Gabriel Mihai,
Thank you for posting your query on Microsoft Q&A.
Based on your description, I understand that you're trying to log in to the ZohoDesk application with external tenant users (from another Entra Organizational directory) and encountering an error message: "AADSTS700016: Application with identifier 'mystore.zohodesk.eu' was not found in the directory 'Default Directory'. This can happen if the application has not been installed by the administrator of the tenant or consented to by any user in the tenant. You may have sent your authentication request to the wrong tenant."
This error can occur if the application is not enabled for multi-tenant support or if consent has not been granted by the resource tenant.
To troubleshoot this issue, please follow these steps:
Verify in the home directory where the application is registered that it supports multi-tenant account types.
Login into Entra ID >> Go to App Registration >> select the app >> Click on Authentication
Once the application is enabled for multi-tenancy, ask the administrator of the resource directory to provide consent to the application first. This can be done using the following URL:
https://login.microsoftonline.com/common/adminconsent?client_id=your_client_id
After the consent is given, try logging in to the application again to see if the issue persists.
If you're still stuck on this, you can feel free to send me an email at AzCommunity@microsoft.com referencing this issue with a subject line "ATTN:pothurajur" include a link to the current thread.
I hope this information is helpful. Please feel free to reach out if you have any further questions.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Thanks,
Raja Pothuraju.