Apologies, on the delayed response.
I play on Android, G22 Ultra and PC through Plarium. The pop up started after the Jetni event started, then there was a quick maintence and it went away. Yesterday, 5/24 it started again and currently I can't log on at all. It now pops up with a Connection Error. Are the servers currently down? If so I'll wait till they come back online to see if this failed purchase pop up error is still going on. Hopefully not because I'm not attempting to make any.