"Unable to connect to the data source" while importing contacts

Hi All,

When trying to import contacts, On click of Import Contacts button in Sugar we are getting "Unable to connect to the data source" popup and import is not happening. It's happening only in a few modules. We tried doing the below things. But still the same error. This is happening in the Production environment.

1. Setting the folder-level permissions to the right level.
2. Restarting the Application server and MySQL services.
3. Rebuilding the cache and running quick repair and rebuild.
4.No errors in console and sugarcrm.log and php-error.log

Could you please suggest us to solve this issue.