Hi,
did you try this? https://groups.google.com/a/googleproductforums.com/forum/?hl=en#!searchin/sketchup/how$20do$20i$20choose$20a$20nickname|sort:date

You need a Google account with nickname. Normally the upload process should offer you a possibility to add the nickname directly but it seems this does not always work anymore. You can choose such a nickname in your Google account settings ("Edit personal information"). For a more detailed explanation, see here: https://groups.google.com/a/googleproductforums.com/d/msg/sketchup/XTbzBBINees/E8YUL3kIvW8J