As a general rule, ALL options must be matched on either side of the VPN.
The exception of Certificate and key, which must be unique to each node.
(unless over ridden by --duplicate-cn)
Please see the various --tls-* options in the manual.
Start here:
HOWTO: For OpenVPN Community Edition
For help Please see:
HOWTO: Request Help ! {2}
(Note: log files)