you will need to scrape the enamel off each strand of the wire. use a knife or sand paper.
I have even had success dipping the ends in a very light solvent like acetone.
Sounds like the enamel needs to be removed. There are some tutorials on this forum. What I remember is aspirin or solder iron heat to remove it. A lighter will not be enough.
@lowGuido was faster. Yeah scraping it off should also work.
Get your iron super hot with a blob of solder on the tip. Hold it for a few seconds and you should see the enamel melt. You need to clean it up and reapply sloder