More often than not, simply logging out and back in will solve this issue, so let's try that first. When you do this, please make sure to close your DAW, then open the standalone Arcade app, log out, and then log back in.
If that step doesn't work for you, you can check out this page for more in-depth troubleshooting steps: Arcade Says I'm Offline When I'm Online
If none of the options in the article solve your issue, feel free to reach back out and confirm all the things you checked and tried. We'll be happy to further assist!