Whether the network configuration is correct: each province has its own server address and port number. If you fill in the form incorrectly, you will definitely not be able to connect to the tax bureau server, which will make it impossible to upload the invoice;

There is an invoice with a blank signature value among the invoices that have been issued, so all invoices issued after this invoice cannot be uploaded. In case of this problem, it is necessary to repair the earliest invoice that has not been uploaded, and then wait for a while to see if it has been uploaded.

If you fix it, the proof won't be the second problem. Please check the first question. If it is not clear, please contact the service unit personnel to solve it remotely.