[A] If you are facing 500 error as shown below, please follow the below steps.
[B] Check the number of the document which you are creating as shown below.
[C] Now check if that document (like PO, OC, Invoice) is already present in your system or not.
[D] In order to check this go to "All Documents" module, in this case, we are facing issue while creating invoice hence "Document" is set as "Invoice".
[E] Now search the above invoice number in all the tab expect cancelled using search box.
[F] If you find the document in any tab that means document with the above number is already present in your system.
[G] In this case you need to add the latest document number from the settings module. If you don't have permission for settings module please ask your management to make the changes
[H] If you do not found that document in that document's section check it in draft section as shown below
[I] If you do not found that document in both the section then please co-ordinate with our live chat agent.