Global search not working for Custom fields of Stock modules

Hi,

We have upgraded our SuiteCRM from version 4 to version 7. We have identified that the global search on custom fields are not working. On the other hand global search on the older version is still working. We have not done anything additional apart from an upgrade and data migration to the new system

Just wanted to get an idea if this is a system issue or we need to take a look into it. Also any suggestion from your side would be really appreciated. Waiting for your response.

Please some one reply ASAP as it is crucial. Thanks in Advance