Ok, you are working in M2020 Student, maybe something was missing when loaded in M2019. And this is my first time with MASH, therefore something of what I suggest might be unnecessary.
So....actually a lot is going on there.
To see why no collisions, turn on BulletSolver>Debugging>Colision Shapes - you have translated pills away manually and collisions are about to happen ..Elsewhere 😄 - looks like nono for me.. And that is just a small fraction of why..
1. Bullet solver transform - reset back to origin (turn back Grid display!), scale 1.0. You don't need floor collider because you have solver's Ground (changed to 0,0,0);

2. main_pill group - rotated vertically, centered pivot, moved back to the origin, froze transformations;
3. Grouped all the geo and lights with pivot point to the floor plane's center and snapped to the origin - less negative calculation values;
4. To speed up sim decreased _Distribution grid to 5x5x5, change back to 8 once you are happy;
5. Added mash_Transform for pills, in Translate entered 100,480,-210;
6. Added mash_Random for pills to randomize rotations.
7. After experimenting with _Dynamics solver I ended up with such ConvexHull shape, and 1.3 scale.
8. You have to set the pipe collider to shape>MASH>Mesh. Even it was done, the bullets still passed through, so I applied meshSmooth several divisions, reversed normals, deleted history, and froze transforms for scale.
9. to speed up sim, ReproMesh Level of Detail can be set to boundingBox, activated UseGPU.
That was it.
,,,_°(O__O)°_,,,
Maya2019.1 @ Windows10 & GeForce GTX1080Ti
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