When you try to open Microsoft Dynamics NAV Web client, you get the following error:
A fatal error occurred. The connection to SQL server cannot be established or is no longer usable.
There can be various causes of this error. The most common causes are that Microsoft Dynamics NAV Server has stopped or the connection to SQL Server is not configured correctly.
Resolution
This error occurs when Microsoft Dynamics NAV Server cannot connect to SQL Server or to the Microsoft Dynamics NAV database. To resolve this error, verify that the following conditions are met.
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Microsoft Dynamics NAV Server connects to the correct database by using the correct login account.
You can do this by using the Microsoft Dynamics NAV Server Administration tool. For more information, see Microsoft Dynamics NAV Server Administration Tool. -
Login account has the following permissions:
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Permission to log on as a service on the computer that is running SQL Server. For more information, see Provisioning the Microsoft Dynamics NAV Server Account.
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Set up as a user in the Microsoft Dynamics NAV database on SQL Server with the following role memberships: db_datareader, db_datawriter, and db_ddladmin. For more information, see Setting Database Owner and Security Administration Permissions
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Permission to log on as a service on the computer that is running SQL Server. For more information, see Provisioning the Microsoft Dynamics NAV Server Account.
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SQL Server has the following configurations:
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TCP/IP protocol is enabled.
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SQL Server executable file is allowed through the Windows Firewall.
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SQL Server Browser Service is running. This is required only when Microsoft Dynamics NAV used a named database instance, such as NAVDEMO, and Microsoft Dynamics NAV Server is on a different computer than SQL Server. For more information, see How to: Start SQL Browser Service.
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TCP/IP protocol is enabled.