iOS client and Files stops working in background

I’m someone will tell me this an iOS thing, but I thought I would point it out and see if there may be a workout.

For my Todo list, I use a bash script called todo.txt. It reads a simple text file that I store on Nexcloud, so I have access to it across all my devices.

On my iPhone and iPad, I installed the Nextcloud app. I setup an app called Swiftodo to read my todo.txt file from Nextcloud through the iOS files app.

When I add tasks on my desktop, they make it onto my phone and vice versa, but only for 48 hours. After that the sync stops working. In those 48 hours, I never launch the iOS app.

Is there some way I can keep this file in sync at all times, without needing to pop the Nextcloud app?