This is rare on GT-P5100 builds. Ensure you downloaded the “espresso3g” version, not “espressowifi”. Try toggling Airplane mode on/off.
To update a Samsung Galaxy Tab 2 10.1 (GT-P5100) Android 7.1.2 (Nougat)
: Moving to a custom ROM will wipe your internal storage.
Ensure your tablet has at least 70% battery. A power failure during installation is catastrophic.