and not an invoice.
That said, the manufacturer wants to see evidence of the model supplied, and of the fact that it really was supplied on a given date, and to a given address.
I suggest that you now deal exclusively with the manufacturer, as they will support their product from here on in. Legally you have a contract with the orignal supplier, and it's up to them to sort the problem out. Where monitors are concerned however, it's common practice for suppliers to refer consumers directly to the manufacturer, and it's in a consumer's interest to do it that way. The necessary repair/relacement takes place faster, and you only deal with one location.
Try talking to the manufacturer and explain the situation - I'm sure that they'll understand.