After you have created your project, go to Share->Disc
Select DVD, notice two fields, Burner Location and Status,
For burning to DVD, the application needs to successfully identify your burner as well as the media(DVD) in the burner.
Check that the burner you are using is successfully and correctly identified in the Burner Location.
After the burner is correctly identified than look for status(it will show status as Ready once everything is right)
If the status still says Media not present, change your media, i.e. DVD(it may be corrupted)
Also make sure that you are inserting the media in the same drive as shown in the Burner Location field, if not, choose the correct drive in the burner Location.
Hope that helps.
If not, please revert back.
Welcome to the forum.
Sorry about the nature of your Project.
I agree with John, regarding the media. I recommend only using high-quality blank media, such as Verbatim, Taiyo-Yuden or Falcon Pro. Brands, such as Memorex, recent TDK, recent Ritek and any store brands are NOT recommended, because they buy the cheapest media each day, and then rebrand it with their logo on the disc. One might get some good discs in a spindle, but might also get some bad media - all in the same spindle, because the media comes from different sources. This ARTICLE goes into more detail.
Now, it appears that PrE is seeing your multi-drive/burner, so parts of this ARTICLE will not apply, but each multi-drive/burner has firmware, burned into a ROM chip in it. Over time, mfgrs. will issue updates to that firmware, so updating it can correct a lot of problems. For firmware updates, the exact steps required will likely differer mfgr. to mfgr., and might even differ between models of burner, or even firmware updates. Read the instructions, until you know exactly what to do, and in what order. I recommend printing out the instructions, to have them to follow, as one updates the firmware. This is very, very important.
Good luck, and let us know if that helps.