Media that shows as Data Protector Foreign simply means that it is recognized as have been formatted by DP, but is not currently in the IDB. Formatting it again will remove any daya from teh media, and enable it to be reused. This should be done manually, as the Automatic formatting will only work with blank media, or, I think, media formatted in this cell
This error
"Cannot write to device ([19] The media is write protected. ) "
means exactly what it says, the tape has physical write-protection enabled. In the old days, there was a write-protect tab on the tape, you move the tab, the media became available. Most modern tapes have an embedded chip, and I am not able to tell you how to disable it this way, I guess, if you had a Web Interface to the library, or are using Commandview TL, you could do it that way