If the upper right of your screen looks like the image above, it's because Firefox's Enhanced Tracking Protection is enabled.
To disable it, click on the shield icon at the left of your address bar, and turn Enhanced Tracking Protection off.
Why do I need to disable it?
Your profile image is loaded from https://pbs.twimg.com/ which is where Twitter hosts the profile pictures.
Since it doesn't match Hypefury's origin (https://app.hypefury.com/),Firefox's protection considers that image as a tracker and blocks it.