Thank you very much for your question!
We've checked to find that you have Pro account now, which makes it possible to sign in to Mac version.
If any further questions, please feel free to contact us.
Nice day!

Ive been having the exact same question. I can signing to the web based version but the native OSX app will not allow me to sign in. I suspect there may be an issue with user names or something . I'd appreciate some help here, too.

@Festus Thank you for your support!
We've checked to find that you have upgraded to Pro account.
If you still could not see the Pro status on your Mac version, please refresh your web version and manually sync your phone and desktop version.
Nice day!