Are you referring to the recording mode (XP, SP, LP, EP, and SLP)?
If so, what are you trying to record from (VHS, DVD, TV, Cable)?
How do you mean when you say, "It doesn't work"? Please provide more details.
Ok. Are you formatting the discs prior to trying to record?
What kind of discs are you using to record to?
What kind of discs are you trying to record from?
How is the DVD player connected to the DVD Recorder?
FiOS DVR isn't going to record if the content is Copyright protected. With my experience there are three modes of HDCP protection:
The first means you can't even copy it using your DVR. This is typically PPVs.
The second means you can use your DVR to record it, but it cannot be transferred or reformatted. This is typically premium channels (HBO/Showtime/Etc...) and some sporting events.
The last means you can record and copy/reformat to your hearts content.
Now I'm not certain with DVRs and they may have their own rules about copying content and this may be what is preventing your recordings or your ability to change the recording speed.
Also, you didn't answer my question about pre-formatting the disc as per pg 28 of the users guide.