This happens because you were probably going to update the firmware from a significantly older version, such as 5.0 to 5.1 etc.
Here is how to fix it.
1. Connect the Gemini-2 to your computer with an Ethernet. Make sure your computer can see the web interface of the Gemini-2. If it can, then close the web interface.
2. Open up File Explorer. In the address bar of file explorer type ftp://admin@gemini
3. This will show you the contents of the micro-SDcard in the main Gemini-2 unit.
4. At the root of the SDcard, if there is a file named HGM_Gem2.bin or CUR_Gem2.bin delete it.
5. At the root of the SDcard, if there is a file named NewGem.bin, rename it to HGM_Gem2.bin
6. Close file explorer. Turn off the Gemini-2. Wait 5 seconds and turn it back on.
7. This should have updated the firmware. If it did, then you need to do step 4 again, and you are done.
8. If it did not fix the firmware, then open up File Explorer again, and go back into the SDcard using Step 2.
9. Delete the file NewGem.bin
10. Now download the firmware from http://gemini-2.com/current/combined.zip and put it into a clean directory.
11. Unzip the combined.zip file.
12. Copy the NewGem.bin file to the root of the micro-SDcard using file Explorer. This is easier to do by opening up two windows of file explorer. Pointing one to ftp://admin@gemini and the other at the unzipped files.
13. Now go do steps 5, 6 and 7.
Note: if ftp://admin@gemini does not work for you, then try ftp://firstname.lastname@example.org or ftp://admin@Your Gemini 2 IP address.