Openvpn server unable to set it up

RouterOS Beginner Basics
1

Trying to create an openvpn server so when i will be out of home, i could join the LAN securely.
i have followed this link to start

https://grzegorzkowalik.com/mikrotik-openvpn-server/

But i am getting the following error:
[admin@MikroTik] /certificate> sign CA-Cert name=CA-Certificate
action timed out - try again, if error continues contact MikroTik support and send
a supout file (13)
[admin@MikroTik] /certificate> sign CA-Cert name=CA-Certificate
failure: name must be unique!
[admin@MikroTik] /certificate> sign CA-Cert name=CA-Certificate
failure: name must be unique!
[admin@MikroTik] /certificate>

i have a dynaminc ip, so i used a ddns name

atuxn0ll.ddns.net

and i am using a pppoe connection to get the public IP directly to Mikrotik.
Any ideas please?

2

It would be easier for you to set up an L2TP/IPsec to connect securely in your Lan.