I see the problem. I'm pretty sure your belt is reversed. The carriage attachments should be below the free belt.

Check out this thing. It shows the correct belt configuration.https://www.thingiverse.com/thing:3676895

Other things to watch for on the i3 Plus:
Y-axis idler twisting - Lots of easy mods to brace it.
X-axis coming loose - I've got a nice X-Z axis rebuild that makes maintenance a lot easier and the printer much more robust - https://www.thingiverse.com/martin_au/designs
Extruder lever wearing out - 3D printed replacement is available in my collection, or you can grab a metal one.
Bed wires wearing where they go through the 20x20mm hole in the Y-carriage. Wrap with some tape, or if possible get a replalcement aluminium carriage.