Alright so I experienced this myself and came across a method without searching that fixed this for me and I wish to share it as a possible guide/helpful solution to others having this issue.
Alright so first of all you want to launch a Backwards Compatible title from your Xbox One Console.
The while in the game hit the two center buttons below the guide button simultaneously to bring up the 360 guide while in the game.
From here you want to hit "X" to sign out then go to manage storage and delete your profile "Make sure it is only your profile not profile and items"
Then from here you can go to the first screen you see after hitting those two buttons to bring up the 360 guide where you would see like your friends messages and such and find the option "Download
Profile" and select that option.
From here you want to enter the credentials for your account and re-download your account then sign in.
If done correctly you should now have your gamerpic showing as well as your achievement score and achievements earned for the games you've played on your account.
I hope this little guide helps those of you who run into this issue as I did.