Would like to ask what are the possible causes for columns of cells in a datagridview not to show values being pushed into it?

I have a datagridview with about 40+ columns and for some strange reason a number of columns are able to accept values I am pushing into them using:

datagridview.rows[rowindexhere].cells[columnindexhere].value = valueToPushHere;

whereas a number of others wont accept it? This is really weird and not sure if there are some undocumented things or limitations about Datagridview control that new users like me need to be aware of to ensure successful push of info into the control 100% of the time?

Thanks so much for all the help you could give ... I really appreciate it.

Gratefully,
Matt