Debug the Sandbox/Test environment in D365FO

 Above mentioned steps can be reduced to only one step i.e refresh of production DB to sandbox via LCS and later we can connect to sandbox environment directly from the development environment for debugging using below guide

Time required 20 minutes.

Steps

1. Enable access for your IP address

   Go to lcs ->sandbox environment page. To connect to test environment RDP, you need to create Whitelist rule for your IP address 

2. Connect RDP and open SSMS
   

   Connect to SQL server using Server name from LCS and add the prefix to SQL server name – servername.database.windows.net

3. Create a new query to test DB

   Below query will create a new user that will be used for debugging
   CREATE USER devtempuser WITH PASSWORD = ‘pass@word1’
   EXEC sp_addrolemember ‘db_owner’, ‘devtempuser’
   
   

4. Whitelist your IP address

   Select new query against Master DB
   exec sp_set_firewall_rule N’DEVNAME’, ‘IP’, ‘IP’ 

5. Stop IIS, WWW service and Batch Service

   Open IIS and stop the service. Open run and enter services.msc and stop WWW and Microsoft D365 batch service
   

6. Edit Web config

   Go to C:\AosService\webroot\web.config and save the original file somewhere else as backup. Modify 4 Keys as per the below screenshot.
   You can either comment original configuration or delete it and add new configuration of the sandbox environment

7. Start IIS and WWW services

   Start IIS and WWW service stopped in step 5. Don’t start batch service.
   

8. Open the development environment AX URL

   If you get 503 unavailable error, go to CMD(as admin) and type IISRESET
   

9. Debug

   Now sandbox environment is connected to your development environment. You can simply open Visual studio to add breakpoints to X++ object and attach w3wp.exe service to debug.

10. Thanks Pawan Deep SinghI 

11. Reference: https://axparadise.com/how-to-debug-the-sandbox-test-environment-in-d365fo/