I am also having this problem. The issue is that I cannot enable 'Tiled Rendering' to allow produce renders larger than 1920 x 1024.
I can see the button, it's right there next to output size, width, height, but it is greyed out.
Also, in the drop down list of 'output size' button, only 2K and custom are available choices, the others also 'greyed out'.
All this is under the 'media > image > image# > format' area.
Am I in the wrong area to change the output size? Has Twinmotion deemed my hardware incapable of rendering higher than 2K and not even allowing the option?
Any help is most appreciated, of course.