I did it on a Kindle.

I'm trying to do it on my phone and it keeps on saying username may not be empty but I'm putting in my username and on the top I'm putting in the id number it gives me in the settings 

The vote login is telling me my ID and Username don't match. I am using Plarium Play on PC. I tried my email in the ID field, and that read as empty. I tried all lowercase on my user name, but that doesn't seem to matter.

Just realized my Forums ID is different from my Plarium Play ID. Checking...

That did it. Check your Plarium Forums ID. That is the number it is looking for.