Can’t Log into Instagram from Multiple Devices

Hi! I’m struggling so so much with this, and it’s driving me mad. Last night I used a third-party app to look at my insights and stuff, but soon after discovered that such apps aren’t always trustworthy, so I logged out, and uninstalled it. I’ve always been logged into my account from my phone and iPad, but ever since last night, I get logged out of one device if I log into the other. It’s never been like this. I was always able to be logged into the account from both devices simultaneously, no problems whatsoever. After I uninstalled the Instagram followers analysis app I changed my password in fear that the app had access to my account. I’ve changed my password again since then, am able to log into both devices but when I’m already logged into one, that one gets logged out if I log in from the other. I’ve enabled the two-factor authentication and everything. Can someone please help me?