UniqueNumbersAPI deleteSequence issue

Support
#1

I try to reset my sequence but I have the following error:
PSQLException: ERROR: relation “seq_un_invoiceregno” does not exist
_ Position: 16_

On the other hand I have an error in PgAdmin 3.

image

Could you give me an example in order to reset (delete) a sequence and explain these errors?
Below my code:

            uniqueNumbersAPI.setCurrentNumber("invoiceRegNo", 2700);
 //          uniqueNumbersAPI.deleteSequence("invoiceRegNo");
            entity.setRegistrationNumber(String.format("%s%04d", "ABC", uniqueNumbersAPI.getNextNumber("invoiceRegNo")));