Read the forums. There are a few issues with the newest release. API Key verification may be one of them.
Patience is necessary for this process.
You can potentially use other versions. I'm on v3.3.2 myself. Others are using 4.0.5 or whatever works for them.
I've read posts in the forum where v5.0.1 didn't work with an API key but other versions worked fine with the same API key.