What browser are you using? Safari and Internet Explorer don't support the export function, so if you're using one of those, try Chrome or Firefox. 😉

I use Chrome

Grouping is there to help reduce the file size. Try exporting with the "Group by Geometry" option. This exports the file perfectly for me on Chrome.

Exporting the geometry is very demanding for the browser and when the model is too big it can crash. It is even worse when you select the logo option. The best solution is to select the collada format with the option "Group by Geometry". It has been designed to avoid the issue with this type of model.