I've used a 'scratch awl' or a cotter pin puller, you may need to get something that comes to a point to get under the clip.
Try prying on it at one of the ends.
This is one of the not so good features of the R65 .
I devised a method a few years ago, to get the clip off.
I used a three jaw puller, turned the jaws around to where they pointed away from each other, wrapped the fork tube with a part of an old inner tube ( this was done with the forks off of the bike), secured the puller to the fork tube with worm gear clamps, tightened the clamps, and used the threaded part of the puller , to push down on the plug, then you don't have to fight the spring tension, while trying to extract the circlip .