Hi Yoz
It’s because you have still a LOT of textures used and the viewer’s not prepared to do OPTIMIZATION to show a full-resolution model. So you need to set an even larger detail to get it done. For presentation it’d work even with a bit lower resolution as it’s for reviews only…
Depending on the project size, I think even 5cm resolution should be OK.
So you need to try out few more settings on UNWRAP with fixed detail and increase it to 5 cm resolution to get a lower texture size… and I highly recommend you to close all applications except the one where you’re opening the 3D model, as it eats the GPU RAM ( even web browsers like Chrome, Firefox, Internet Explorer etc. )