scams, you do not know how many clients mess I have had to clean up because of this.

Respond to the email that you didn’t change your password. Then, if you can, change your password. You might also change your email password.

My Amazon account was hacked back in March. Im still dealing with the fallout from that.

which is a dead/removed site.

I’ve had for 10 years. I keep it just so I can refer to my order history but I can’t use it. Every time I log in there’s 30+items in my cart that total thousands of dollars...just waiting for my credit card to be entered. I’ve changed passwords, use two step authentication and it just keeps happening. I opened a second Amazon account with a new email and it has not been a smooth ride either. If you ever are able to access your account, I recommend never keeping a credit card on file with Amazon.

Could be something like a phishing attempt if it demands an action from you by logging in while it redirects you to another site.
As a general rule, never use any links from a mail you received, only the official links. I assume you can still change/test the password yourself.

Try signing in with the same password you had, but definitely not by clicking on a link from that Email. Use a fresh browser and Instagram’s own signin page.

If it works, and it probably will, that Email was a scam to get you to provide personal info to some shady group. Often these groups harvest personal data and resell it in large sets to actual criminals.