Error when trying to change a users role

I am using mySQL as my database and authentication store. The tables were set up using the WAT. I am trying to change a registered user's role once verification is completed for their application for a higher level of access. I am doing so in an admin page. The code behind when the update is clicked is as follows;
Protected Sub gvPendingUsers_RowCommand(sender As Object, e As GridViewCommandEventArgs) Handles gvPendingUsers.RowCommand If IsPostBack Then If e.CommandName = "ApproveRegistration" Then Dim index As Int32 = Convert.ToInt32(e.CommandArgument) Dim row As GridViewRow = gvPendingUsers.Rows(index) Dim imgbutton As ImageButton = TryCast(gvPendingUsers.Rows(index).Cells(6).Controls(0), ImageButton) imgbutton.ImageUrl = ApprovedUrl Roles.RemoveUserFromRole(row.Cells(1).Text, "pending") Roles.AddUserToRole(row.Cells(1).Text, row ...