Using Jira 6.3.6 I have not been able to import "Original Estimate" using for example attached files. The issue is created successfully (no errors in report either) but "Original Estimate" field in the finished user story in Jira is empty although I could see the value "21600" while performing the import steps. I have followed the guide in:

• https://confluence.atlassian.com/display/JIRA051/Importing+Data+from+CSV
• https://confluence.atlassian.com/display/Cloud/Creating+issues+using+the+CSV+importer

"The value of this field needs to be specified as number of seconds." which I have specified it as 21600, which is 6h.
I can't import "Remaining Estimate" or "Time Spent" either, all other fields of interest for me is no problem to import.

Workaround:

Use the CSV import option detailed here:

• For JIRA Cloud
• For JIRA Server