Well, I don't have a contract, as such, with either client, but only a purchase order. One of the purchase orders says that "invoices will be submitted via our on-line system" and then gives a link to connect to their system (which doesn't work), but the purchase order doesn't say that this is "of the essence" or anything like that.
The agency also wants me to upload my translation via their on-line system, but when I can't do that, is quite happy to accept it as an email attachment - so - having it both ways?? (i.e. their system necessary for receiving invoices, but not essential for receiving the work itself).
Thank you, ***** ***** is helpful. I'll make a further attempt to explain to both customers that I've made every effort to send my invoice via their system but that I can't make it work. I haven't even sent either invoice yet, which is what worries me a little (the payment isn't "late" yet). Then I'll send the invoice to them as an email attachment and wait and see what happens. If they still reject the invoice, I may need to ask further questions about this in due course. If so, can I re-open this question?
Thanks for your help.