I have two systems, both ground-up builds, identical Win 7 Home Premium and Premiere Elements 12 installs. Both systems have internal blu-ray burners. One burner is an ASUS BW-12B1AT and the other is a Pioneer burner (don't recall the model number).
System 1: Intel 4770k with Gigabyte MB
System 2: AMD 8-core with Gigabyte MB
System 1 gives "Media not present" error in PE12 when attempting to burn to blu ray discs using Verbatim discs. System is able to burn DVDs and CDs, and playback blu ray discs. System is also capable of burning blu rays using Nero.
System 2 works fine - blu ray media is recognized instantly by PE12 when in the drive and burns blu rays perfectly.
I swapped the blu ray drives and SATA cables from System 1 and System 2 with the same result - this eliminated the drive manufacturer and cables from being the problem, as both drives worked perfectly in System 2 and neither worked in System 1. I also tried different SATA ports and power supply taps on System 1 without any success.
Then, I noticed that on System 1, with the dialog box open and indicating the "media not present" error, if I ejected the blu ray disc and reinserted it, the burner LED would flash 18 times (approx. 1/sec) and then pulse briefly indicating a burst of activity for about 1 second, as if it was either reading the disc or writing to the SATA. If I pressed the "rescan" button during this brief burst of LED activity, then the disc was recognized and I could proceed to burn it. If I tried to press the rescan button at any time before this instant or after, the "media not present" error did not clear.
To me, this is an indication that something in the handshake timing of the SW and the burner is not correct, and that timing differences in the system HW are not provided for in the SW. I see that many others have had this issue and have had to buy work-around image burners to address this. I believe your burner drivers need to be reworked to eliminate this bug. This is evidenced by the fact that Nero works and your SW does not, and that different systems consistently exhibit this problem.
Please let me know when you will have a SW patch to address this or if you have any idea of system settings that can be adjusted (I don't know of any myself) that would eliminate this problem.