If you’ve already sent the chat without media and it’s still incomplete, you’ve probably reached the limit for the WhatsApp chat export with Android. Unfortunately, Android limits the export to the last 40 thousand messages. This is a limit we cannot influence. However, there are different options to work around it:
In case your chat partner has an iPhone you could try to export the chat with it. With an iPhone, it’s no problem to upload the whole chat.
Have you exported the chat to yourself via e-mail earlier? It would then be possible to merge the two parts.
You could copy the messages from web.whatsapp.com and upload them to zapptales. This is how it works: