All public firmware is posted at
https://tsd.dlink.com.tw/I looked up this model and B3 was designed for EchoStar (ES) - Hughes.net ISP and they lock the firmware so you cannot load non-ES firmware. Firmware updates were from the ISP.
Did you buy this router from 3rd party/ebay?
You can possibly try a crash recovery/emergency firmware upgrade:
1. From the link above, download a rev Bx or B3 firmware for the DIR-619L and unzip it (if zipped).
2. Unplug the cable from the Internet/WAN port.
3. Turn off the router. Hold in the reset button with a paperclip and then power on while holding the reset button down.
4. Wait about 10 seconds and release.
5. Statically assign your computer an IP address of 192.168.0.2 / 255.255.255.0.
6. Open a web browser.
7. Go to http://192.168.0.1. The Firmware Recovery page should appear. If not, Try step 3 again. Note this may take a few tries to work.
8. When completed, the router should reboot. You can then set it up from scratch.