See if its mentioned clearly that you need to upload the caste certificate after 1st April then you need to make a new one. But as per the information available, there are no such instruction regarding the OBC Certificate. I think you are mixing it up with EWS certificate. For most of the examination the EWS certificate is required to be issued after 1st April. So it would be better for you if you can recheck or confirm through the UPCET helpdesk.

You can get the contact details by following the link below:

https://upcet.nta.nic.in/WebinfoCms/Page/Page?PageId=2&LangId=P

To know more about the UPCET visit the link below:

https://www.careers360.com/exams/upcet

I hope this answer helps. All the very best for your future endeavors!