I tried rebooting my
phone. Removing and reinstalling Instagram. I found info on the web that says
it's a bug. I tried logging in with my
username and password. I tried logging in using the Facebook log in option.
Whatever I tried, the problem persisted.
Until now. Maybe
it's just coincidence, but this is what I did.
- Launch Instagram and log in, if necessary.
 - Press on your profile thumbnail at the bottom right.
 - Press on the gear at the top right.
 - Scroll all the way to the bottom.
 - Choose the option to Log Out.
 - When prompted to remember your log in, choose Not Now.
 - Confirm by pressing on the Log Out option.
 - Log in again.
 - Log out again, but this time choose "Remember".
 - Log back in.
 
If this worked for you, please let me know in the comments below, and feel free to share the solution with others.