When you do bulk insert in SQL Server it may fail with below error because of double hop .
Msg 4861, Level 16, State 1, Line 3
Cannot bulk load because the file “\\path\” could not be opened. Operating system error code 5(failed to retrieve text for this error. Reason: 15105).
Steps to fix the above error
1. Connect to SQL Server using SSMS (With account you run bulk insert) and execute below query and check if it is using Kerberos authentication
select net_transport,auth_scheme from sys.dm_exec_connections where session_id=@@spid
2. If the session is not using Kerberos authentication then fix the SPN issues (startup account of SQL Server should have read and write SPN permissions). Account which is running bulk inser should have read SPN permission. Setpn exe or adsiedit can be used to add or display all the SPN’s. If the SPn’s are registered properly and still connection fails to NTLM then get the output of SSPIClient.exe and verify why Kerberos authentication fails.
3. Make sure the account which is running bulk insert is trusted for delegation in Active Directory.
4. Account which is running bulk insert should have access to the shared directory in which BCP files are placed.
Reference BULK INSERT (Transact-SQL)
Security Account Delegation (Impersonation)
If a SQL Server user is logged in using Windows Authentication, the user can read only the files accessible to the user account, independent of the security profile of the SQL Server process.
When executing the BULK INSERT statement by using sqlcmd or osql, from one computer, inserting data into SQL Server on a second computer, and specifying a data_file on third computer by using a UNC path, you may receive a 4861 error.
To resolve this error, use SQL Server Authentication and specify a SQL Server login that uses the security profile of the SQL Server process account, or configure Windows to enable security account delegation. For information about how to enable a user account to be trusted for delegation, see Windows Help.
For more information about this and other security considerations for using BULK INSERT, see Import Bulk Data by Using BULK INSERT or OPENROWSET(BULK…) (SQL Server).