NDVI not working

Does the snap allow processing of Landsat?
I get error specified region must intersect with image bounds when processing ndvi with landsat 8

In general snap can process landsat data. But currently there is a problem in the beta 5 version.
To work around this you have to choose either Landsat8 in 15m (GeoTIFF) or Landsat8 in 30m (GeoTIFF) from the menu (Import --> Optical Sensors --> Landsat).
You can also use the open dialog and choose one of these formats in the dropdown box.

Currently we work on the issue to support products containing bands of multiple resolution. This is where the problem comes from.