When you select the modeling method (from Simulation Options) as Non - Linear, Large Deformation gets enabled. Though this cannot be directly checked in Discovery, if you transfer the model to Mechanical, you can see this option enabled in the analysis settings.
The model is getting converged using below mentioned settings:
1. Stiffness factor = 0.01
2. Detection radius factor = 1
3. Initial, minimum and maximum substeps were set as 20,20 and 200 respectively.
4. The top face of the support was split and a couple of faces were included in the contacts.
Below is a snapshot of the deformation of the buckle.
I am also attaching the project file for your reference.