Instafeed is broken on the demo site.
I also couldnt get it to work on my own site. I found the documentation (https://joomlead.com/g5/docs/instafeed-particle/) but thats look a bit outdated. Filling in the username should be sufficient right?
JoomLead Gantry5 Particles 2.2.8 released, new features, bug fixes and moreLearn more
Flash Sale. Get Up to 25% Off - Coupon: FLASH25Shop Now