We can't tell you what you or Cloud has done "wrong" from that description. "However, it showed an error regarding the license activation." is a bit like saying "my car won't start" - we don't know if you've lost the keys, dumped it in a river, run out of fuel or been attacked by a horde of annoyed penguins and can't get to it.
Your best bet is probably to contact https://support.atlassian.com and tell them your Cloud account details. They can tell you what is wrong.
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