why can't I enter codes to sync?

I have installed Firefox on my Android phone with no problem. When I go to sync with my mac, I get codes, just as shown in the walk-thru. On my phone I also have a code. On neither device can I type in a code, overwrite what is there, nor is there a place to enter a "new" or alternate code. My computer also says that I already have an account set up, yet when I try to use a recovery key (several times) it says "invalid key". I have then tried to update the key, or get a new key, to no avail. I know it is not this hard!!!