Squential Printing: Some objects are too tall and cannot be printed without extruder collisions The following setup seems printable.
Why do I get this error?

Some objects are too tall and cannot be printed without extruder
collisions.
The error message explains that you cannot print your objects sequentially as they are too tall for the gantry to go back to the bed level after the first object.
In other words, your clearance between bed and gantry is too small.