Unable to read a disk that has not been finalized unless new

My recorder is about 8 years old. It has started to say that when I put in a disk that has some recordings on and want to finish the disk and close it out, that there is not disk in the machine. If I put in a new disk and start recording, I have to complete all that I want to put on it and finalize the disk before I shut down the machine or it will so no disk in machine when I restart it.