@Manuel-Doming 

Hi,

I don't know what prevents your OpenVPN server from working, but I'd like to let you know that despite CanYouSeeMe saying "Error: I could not see your service on **** on port (1194), Reason: Connection timed out" the OpenVPN server running on port 1194 on my Archer router is working just fine. 
So, you can neglect what CanYouSeeMe (and other port checkers on the Internet) say.

Have you already tried whether the WireGuard server would work on this same router?
 

Hello @woozle,

thanks for your reply. Yes, WireGuard works great and I have the client set up on my smartphone precisely because the OpenVPN server doesn't work. It really frustrates me to have a new router where such an important feature for me like the OpenVPN server doesn't work. At least, as you mentioned, I can connect using WireGuard, but even so, I think everything should work properly.

Thanks again.

  @Manuel-Doming 

Recently there was another user facing an issue like yours. Unfortunately, that thread ended without a final conclusion. Perhaps you can post a comment there in the hope that user might reply to you with a solution.

https://community.tp-link.com/en/home/forum/topic/744470

  @woozle Thank yoi so much. I'll do it, although It seems that nobody is going to give an official solution. I'm starting to understand that I should have bought an Asus instead of a TPLink. The firmware of my Archer AX72 Pro, that is the latest version, seems still a beta product. 

Thanks again.