I can't purchase anything on play.google. I get error "error retrieving information from server [DF-RPC-01]" It's not just in the play store, it doesn't work on mobile or on PC, and I also can't do any in-app purchases in any app.
I tried reinstalling apps, clearing phone, but I believe it has nothing to do with the phone because it's not working on PC as well...
If I go to google payment center, I get "You haven’t signed up to pay for any Google services yet", and I successfully bought an app a few months ago.
This usually happens for one of two reasons:


The payment information registered to your Google account is invalid and causing problems.
The application data of the Google Play Store is corrupted


Managing your payment information

Verify if your payment methods are still up-to-date in Google payments center and in the account section of the Google Play Store. Note that they should match the personal information of your Google account.

Clearing the Google Play Store cache


Open the Settings app.
Click on Apps.
Select Google Play Store from the list.
Click the Force stop button and confirm. The application is now forcefully closed.
Still in the same window, click on Storage.
Click the Clear cache button.
Now reboot your phone and try again to see if the problem went away.