@Rodneymf 

Hi,

Are you saying you have enabled the OpenVPN server of your Archer C7 (V4?, V5?) router and now want to connect to it via an OpenVPN client installed on a smartphone with its own 3G/4G connection?

If yes and if your C7's configuration webpage looks like the screenshot below, then please tell us the first two numbers of the Internet IP address (circled in red).

Furthermore, open the OpenVPN configuration file with a text editor and verify that the line "remote MyHostname 1194 udp" does indeed contain your Dynanic DNS domain name.

  @woozle 

Archer C7 is version 5.0. 

The first two numbers of my IP address are 212.56

However the config file has the following line (without inverted commas)  “remote 212.56.XXX.XXX 1194” so it appears to be lacking some info.

Incidentally, my connection (copied from old original router) is PPPoE.

  @Rodneymf 

Connection type PPPoE is fine.

If the line “remote 212.56.XXX.XXX 1194” doesn't include the protocol type, then your ovpn file probably has a separate line "proto udp" in it (or "proto tcp", if you selected tcp in the configuration). Just check it youself.

What is important is that the Internet IP address shown in the router's "Network Map" menu is absolutely identical to the IP address in the ovpn file (“remote 212.56.XXX.XXX 1194”).

In case the IP address of your Internet connection is not always the same, but changes every so often, then you would need to work with a DDNS domain name instead. 

Below is an example of a log from the OpenVPN client app on an Android phone that shows a properly working connection to a TP-Link AX50 router.

Can you maybe identify at which point your's goes wrong?

  @woozle 

The log agrees up to the point where the Peer info is listed.  The Peer info all appears to be the same but the next four lines are where it goes wrong:

14:20:49.883 -- VERIFY FAIL: depth=1, /C=CN/ST=GD/L=ShenZhen/O=TP-Link/OU=SOHO-I18N/CN=TP-Link CA/name=EasyRSA/emailAddress=xxxx@xxxx, signature: RSA-SHA256 [certificate is not yet valid]

14:20:49.991 -- Transport Error: OpenSSLContext::SSL::read_cleartext: BIO_read failed, cap=2576 status=-1: error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed

14:20:49.992 -- EVENT: CERT_VERIFY_FAIL info='OpenSSLContext::SSL::read_cleartext: BIO_read failed, cap=2576 status=-1: error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed'

14:20:50.001 -- EVENT: DISCONNECTED

14:20:50.001 -- Tunnel bytes per CPU second: 0

14:20:50.002 -- ----- OpenVPN Stop -----

There appears to be a problem with the verification of the certificate.
 

  @Rodneymf 

If that is the case, then create another new certificate via the OpenVPN menu of the C7 and after the process has successfully finished export a new ovpn configuration file and import that into your Android client.

Given the message "[certificate is not yet valid]" from your OpenVPN log it might also be a good idea that you first go to the menu "Advanced" > "System Tools" > "Time Settings" and verify that the router's current date and time are correct!

  @woozle 

Thanks for your patience and help.  At last I have connected.