The following error is shown when trying to access customer's site with database:
Microsoft OLE DB Provider for ODBC Drivers error '80004005' [Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified
On 64-bit Windows systems application pools are configured to run in 64-bit mode by default, however this site needs 32-bit mode.
Go to IIS Manager, find the application pool where this website is located and set the parameter
Enable 32-bit Application to True.