my instagram doesn't connect to fb.?

[Maddie]

i uninstalled instagram. then installed again. thought of doing this as someone suggested:
"I figured it out. What you need to do is uninstall instagram. Install it again. When you open the app, tap on register. Then click use Facebook info. Allow Facebook to use instagram. Then go back and sign in with your instagram username. This should work since I had the same problem! Hope this helps!!"
but then when i clicked "use facebook info" after installing, the same old error message pops up. HELP PLEASE

[Daniel Stromness]

Check if your Facebook is connected to a different instagram account. If so, delete it and try again.