I encounter the same problem with a 18.04.02 LTS version with a OpenVPN 2.4.4.
After speaking with OpenVPN support, sending them logs, etc... They informs me that OpenVPN version 2.4.x prior to the 2.4.7 have a bug that prevents OpenVPN to detect disconnection and so does not reconnect to VPN server on connection loss...
Solutions explained by OpenVPN are :
* run a script by a cron to check connection, and restart OpenVPN if connection is loss
* compile the 2.4.7 version and upgrade to it
* go back to a 2.3.x version that does not have the problem
I encounter the same problem with a 18.04.02 LTS version with a OpenVPN 2.4.4.
After speaking with OpenVPN support, sending them logs, etc... They informs me that OpenVPN version 2.4.x prior to the 2.4.7 have a bug that prevents OpenVPN to detect disconnection and so does not reconnect to VPN server on connection loss...
Solutions explained by OpenVPN are :
* run a script by a cron to check connection, and restart OpenVPN if connection is loss
* compile the 2.4.7 version and upgrade to it
* go back to a 2.3.x version that does not have the problem