I have the same issue , basically I can't play anymore. This is the error after the update is downloaded 100%

"Uncaught (in promise) DownloadInstallerRequestHandler failed", source: https://cdn-gpd.x-plarium.com/browser/content/plarium-play/desktop-update-pages/main.js?8875f38a48c1c294630f (4) 

Having the same issue, click the upgrade button and the button seems to show a progress bar that jumps all over the place, but ultimately nothing happens.  Tried dowloading and reinstalling, but encounter the same issue.

Worked for me this way:

- Uninstall Plarium play and Raid from Applications

- Go to /users/username/Public and delete Plarium Play from there

- Run the Plarium Play installer again

WARNING: these steps will delete the cache and the Raid instalation from your Mac meaning you will need to login your account and install it again 

@dnykcu Thank you for that information - this also worked for me! Once the installer finished, I received the same orange update bar, but this time it completed and re-launched the installer and the login screen appeared after.

@dnykcu Thank you for the help. I tried and it also worked for me so thank you very much.