Good Morning!

Thanks for your post Jeancom.

The most common reason for the error is when Sage 300 CRE is installed from an incorrect location, network share, or mapped drive. 

 Do not map a network directly to the 9.5 folder and/or verify that you are installing from the appropriate location:

• A network drive mapped to the Timberline Office shared folder (a drive letter mapped to \ \[servername]\Timberline Office)
• Preferred:  The UNC path to the server's client installer at \ \[servername]\Timberline Office\9.5\Accounting\Wininst\install.exe.

If this is the reason I recommend checking out article 17086 which outlines instructions on how to uninstall and reinstall properly.  There are two other possibilites that you can look at as well which are article 25025 and article 27219 (as a las resort). 

Hope this helps!

Wendy