I received this quick response that solves the issue - thanks.
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Thanks for contacting Sportsmobile Forums support. Post #4 in the Forums 101 thread addresses this:
https://www.sportsmobileforum.com/fo...1-a-16311.html
We have to do this for you.
What username would you like?
You can check to see if your desired username is available by clicking on "Community" in the blue tool bar on any forum page. Then click on "Member List".
Best Regards,
Social Knowledge Support Team