The generation system may prevent your browser from exporting your precious proposal in case the file is very large i.e. more than 10Mb in size.
In this case, it's very simple.
1/ Click on the open button of your editing tools, arrow on the top right:
2/ Then, you just have to select in "File" then "Download" the type of export you want to do.
If you have any questions don't hesitate to write to us via the Support chat on the bottom right of the page.