Error from task 8212

Hello Ali,
thank you for your message.

May I ask, you have a model in CellBlender (a .blend file) or MDL files?

What specifically the error message says that you have an object that has a certain number of triangles (sides) - 775 in this case.
A surface region (d000_end) is defined using a list of indices of these triangles counting from 0, so the only valid indices that one can use are 0..774.

To solve this problem, in CellBlender, you can redefine the surface region (https://mcell.org/tutorials/surf_class_surf_mol.html#creating-and-assigning-surface-regions), or you would need to find this surface region d000_end in the scene.geometry.mdl and modify it so that it uses indices that wre within the allowed range.

Hope this helps,
Adam