FirebaseDB error: null object reference en cuentas de alumnos, funciona en la del profesor

Hello, we are a group of students and we have a problem with FirebaseDB in App Inventor.

Our project saves data in Firebase and works perfectly in our teacher’s account.
However, in all student accounts we get the following error:

"Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference"

We already checked:

  • Firebase URL and Token: both are correct.
  • Firebase rules: .read and .write set to true.
  • Blocks: they are correct and identical.
  • We tested in different browsers, devices, and Companion versions.

The project is exactly the same, but in student accounts it fails while in the teacher’s account it works fine.
We suspect this may be a server/cluster issue in App Inventor.

Could you please help us check this bug or move our accounts to another server?
We can attach the .aia file so you can reproduce the error.


Hola, somos un grupo de estudiantes y tenemos un problema con FirebaseDB en App Inventor.

Nuestro proyecto guarda datos en Firebase y funciona perfectamente en la cuenta de nuestro profesor.
Sin embargo, en todas las cuentas de los alumnos aparece el error:

"Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference"

Ya revisamos:

  • La URL de Firebase y el Token: están correctos.
  • Las reglas de Firebase: .read y .write en true.
  • Los bloques: funcionan bien.
  • Probamos en distintos navegadores, dispositivos y versiones del Companion.

El proyecto es exactamente el mismo, pero en las cuentas de los alumnos falla y en la del profesor sí funciona.
Sospechamos que puede ser un problema de los servidores/clusters de App Inventor.

¿Podrían ayudarnos a revisar este bug o mover nuestras cuentas a otro servidor?

You may need to check with your IT people that their network is not blocking something ?

Are you actually using a firebase project for your data, or just the MIT provided one ?

It does not seem to be a network-related issue, as both the professor and the students are connected to the same internet environment without restrictions. Additionally, we are using our own Firebase Realtime Database instances rather than the MIT-provided server.

The application functions correctly when connected to the professor’s Firebase project; however, it fails to work when using our individual Firebase projects. This suggests that the issue may be related to project configuration, permissions, or database settings rather than network connectivity.

I’m absolutely not an expert on cloud stuff, but please take a look here: is something that can help ? (the professor’s app works, while individual ones not )

Are your projects running on Firebase's US-Central server? The Firebase component will not work with projects on any other regional server.

You could always test connectivity to firebase using the web component, that might help to narrow down where the problem is: