How is it stuck? Are you trying to get to the embedded portal or to the provider portal? You can try flashing factory image, I'll publish here how to do it but it's on your own responsibility
that you have MAG 250 and NOT the 254, 255, 322 etc. ! ! ! ! ! ! If you'll do it on the other MAGs, it will brick them!
1. Find a pendrive with FAT32
file system format or format one to it. It's recommended for pendrive to have only one partition.
2. Download file Bootstrap_250
and rename it to Bootstrap
3. Create directory mag250
on the partition and copy the file to it.
4. Download file imageupdate
and copy it to the same directory.
5. Make sure
that there are two files: Bootstrap
on the mag250
directory in the pendrive!!!
6. Connect pendrive to the rear USB socket (it has to be rear one!)
7. Plug in MAG 250 to the electricity supply and enter the bootloader menu by holding the MENU button on RC as soon as you've plugged STB in. Do it until you will see the blue screen with some text.
8. Select Upgrade Tools
by pressing Up and Down buttons on RC and enter it by pressing Right button.
9. Enter USB Bootstrap
by the same way as at 8. point. Confirm it by pressing OK.
10. Wait for updating finish. STB will be rebooted and you will see the embedded portal.
If you are connected to the external portal, save the URL of it
because you will lost it, the same with everything you have on STB.