Hi, and welcome!
I think I know what you mean.
I have a similar issue on my V6. The bumper has drooped or dropped forward, and there's too large a gap between the front edge of the bonnet and the top edge of the bumper by the Mazda logo - is that what's happened with yours?
Assuming the bumper wasn't damaged in some way when it was taken off, probably when refitted it hasn't been realigned properly or bolted tightly enough to the frame of the car, or on the rear corners (the pointed parts of the bumper which point towards the back of the car, and screw onto the wheel arch).
I suggest the solution is to dismantle again, check nothing is damaged or bent on the back side of the bumper, and that the bumper hasn't been left to twist out of shape while it was off the car (the sides are quite flexible), then refit as tightly as possible.
Basically someone hasn't taken enough care with the refit. If this was done by a professional bodyshop or garage, take it back and complain!
It's not difficult to take off the bumper yourself and check everything, but best go back to whoever did it first. But if you decide to do it yourself, come back here and we can give advice / post photos.
S