not connected to a company

Dear All,

What are the main causes that make the VB addon can't connect to company database or database server ? This issue escalated by a certain client. The addon in the workstation client can't be open with error message "

1 .restart add-on , 2. log-off company 3. continue working without add on

if oCompany.connect is not skipped. If skipped, it is worked but when attempting to run one of addon features (from a button), the error message "not connect to a company". How to solve the problem ? is it caused by upgrading result ? because the customer has upgraded the PL 20 to PL 41 of SAP B1 2004A version.

I appreciate your answer. TIA

Rgds,