it would help to have the error message with line number, but I'll take a shot at it.
First of all, for next and prev page, you need to capitalize the o and p, so it would be [Let['O']] and [Let['P']]
Enter, esc, ctrl, alt, and shift all need to be set up properly. i'm not 100% sure, but I think its [Enter], [Esc] [Ctrl] [Alt] [Shift]. Check with Blizz on these ones
And for comma, its [Comma], not [Let['Comma']]