RG500Q-EA Arcadyan AW1000 Network registration issue

Modem detects all sim cards, but fails to register on network. I have tried reflashing RG500QEAAAR13A01M4G firmware, but still having the same issue. I have read in the forum that downgrading to R11 firmware fixes this issue.

Please help me with this issue and kindly send the firmware to dinura98@gmail.com