It’s hard to tell really, but your flint looks a little dull. Here’s my method for sharpening flints and it’s similar to what some others have described. Those goofy little brass hammers and whisk brooms don’t work for me.
First, I take the flint out of the cock and place it on a flat surface. I use a small screwdriver, turn screw, nail or something similar. I’ll turn the screw driver blade sideways and place it about a millimeter (or less) onto the edge of the flint and press down taking off small flakes which you can see in the picture.
These flints are very sharp after this! Here’s the flint in my Chambers lock.
Here’s a short video using one of the flints I sharpened using this method. Please pardon the shaky one handed stuff.
Also, I always start with a clean, dry bore when shooting. NO OIL.
Four things I learned helped me more than anything :
No oil in bore
Use sharp flints
Use real black powder
And, if you can swing it, get a gun with a traditional, flat faced breech. It will make life much better.
Hope this helps.