I have some more time so I'll write everything that happened to me
First I wrote to
support@testsys.com email as the error message suggested, they forwarded me to pearson vue technical support. I wrote to
pvsupportdesk@pearson.com and was forwarded to my local pearson vue support center. As there's no pearson center in my country I decided to write to the uk site, I received an auto response that this email box is not actively checked so I started calling... I called the UK Pearson VUE number +44 161 855 7459. I called them once and on my first call. After somewhere around 30 minutes of explaining what happened, a technician initiated a conference call with some other guy that confirmed that "candidates are having problems uploading their assignments" - he said he would create an issue and someone should write an email to me describing the steps I should take to upload the assignment and said that this mail should reach me within 48 hours. Unfortunately nothing happened for the next 48 hours so I started calling again... This time I spent over 2 hours on the phone overall, the call was disconnected two times, I had the pleasure of talking to at least 5 different people, with some of them more than once (front consultant Chris which I would like to greet from here
). One of the technicians was a hindu woman that completely didn't understand what the hell I wanted from her, she decided to transfer me to someone else and after several minutes of waiting for someone to pick up, the call was disconnected. I was really frustrated then. On my third attempt this day my call was directly forwarded to a female consultant in US and she finally seemed to care about my problem, she showed some interest and after around 45 minutes of explaining the problem and confirming my identity she gave my the voucher number over the phone for 1Z0-844.
With that voucher I was able to upload the file and am currently already after the essay part.