sh33p0mat, Have you set VPN to start in libreelec before kodi using the VPN manager monitor tab.
Connect VPN before Kodi starts (LibreELEC only)
Modifies the start up procedure of LibreELEC to start the VPN connection at the same time as Kodi. Requires that at least one connection has been validated.
Be aware that if your openvpn connection takes a long time to connect then it maybe that Kodi starts up before the openvpn connection has been established. I don't see this on a wired network using PIA but your experience maybe different.
Once Kodi and subsequently the add-on has been started, if an openvpn task is found to be running a notification will be displayed to inform the user a VPN connection is running. If no task is found, and there is no VPN connection then a further attempt to connect will be tried (with the usual set of notifications or connecting and success or failure).