EddieS is right on this!
Make sure you spray some lubricant into the connection about 15 mins prior to attempting to replace the filter. There is road gunk, sand, etc that will prevent the tool from being able to fully slide into the connection and release the line.
A couple years back, I tried the plastics and metal tools with no luck until I did this. I did however find the metal tools to work better than the plastics.
Good luck!