Cannot check box in DataGridViewCheckBoxColumn?

The table itself may be set to Read-Only even though the checkbox column isn't the table setting will override the column setting.

I had the same problem, the solution for me was to change the

"EditMode" from "EditProgramatically" into the default of "EditOnKeystrokeOrF2",

this solved my issue.

All the above suggestions were already implemented.

Kind Regards Heider

Just change the readonly property of DataGridView

     MyDataGridView.ReadOnly = false; 

The code seems to be fine, so I just can tell you to check and ensure that the following DataGridView properties are properly set: ReadOnly set to False and Enabled set to True.