Marketplace will start a transaction but won't complete it. Even after restarting MCPE, error persists. I opened Google Play and launched MC directly from there and still received this error.
UPDATE: Bug delays purchases up to a half hour. Just received my purchase.
Thank you for your report!
Issues such as these are often due to a temporary service outage, and should be back up and working again soon. Please keep an eye out for messages from @MojangStatus on twitter for the latest status updates.
For any issues with your specific account or billing, you will need to contact Minecraft Customer Support directly, who will be able to advise you individually.
Quick Links:
📓 Issue Guidelines – 💬 Mojang Support – 📧 Suggestions – 📖 Minecraft Wiki