Copy protection on VHS tapes was accomplished by something called Macrovision. It's archaic enough I won't explain it. You can read up on it yourself if you like. But the tl;dr version is that it weakens certain sync signals in the video signal, causing the image to distort if copied.
Most VHS to DVD copying machines will detect Macrovision, conclude you're trying to copy a copy-protected VHS tape, and give you the error you're reporting. If this is a home video VHS tape (instead of a tape really protected by Macrovision), then it's probably old enough that the signal has faded sufficiently for the VHS to DVD machine to improperly think there's Macrovision on it.
You can try copying the VHS tape to another VHS tape, then running the copy in the converter machine (this will not work if there's really Macrovision on the tape - the VHS copy will be all distorted, so don't bother trying). Or you can hook up a regular VHS player to your computer using an analog video capture device to convert it directly into a MP4 file (which you can then convert to DVD). Those usually have RCA inputs, and plug into the computer via USB. I believe Macrovision messes them up as well.