Unable to view backup image from different master server

We took the backup at Site B –STHQ...... –With Site B Master server –STHQB......  and our expectation to see this backup from different server –Site A Database server –using the Site A –Master server. But it is not working and we are unable to see the images of site A master server from site B master server, well port communication, host entries and other fundamentals are covered. what could be the cause?