Error while posting a sales invoice

Hi everyone,

I am trying to post a Sales order and getting the following error:

The Sales Invoice Header already exists. Identification fields and values: No.='103026'

I checked the Series no. in the setup, the last No. used is 103025…
I tried to debug the code, the debugger stops at the following piece of code:

IF NOT InvtPickPutaway THEN

Can anyone help me figure out the origin of this error???

Thanks in advance

Check in Posted Sales Invoices whether that invoice is already exist ?

Check whether somebody has change the no series?

Finally go to sales header table and look at the field Posting No and remove the value from there and try to post .