Restarting explorer.exe is a quick fix that's meant to be temporary. The problem just disappeared for me and now everything works fine. Sorry I can't tell you what fixed it, I didn't do anything :/

Restarting Windows Explorer seemed to work for at least 15 minutes (then I had to restart for some drivers). Still not ideal though.

Yep, any permanent solution yet?

Some other forum posters and I also have this problem. Pinning and unpinning does nothing until a reboot or restarting the explorer.exe process.

This is a very annoying bug for when you're trying to customise a fresh install and have loads of things to pin.