Troubleshoot ovpn outbound client

Turris Omnia
OpenWrt omnia 15.05 r47055 / LuCI 49c3edd5861fd032fa8379ceda525c27a908a114 branch (git-17.212.24321-49c3edd)|
Kernel 4.4.119-082ea0f4a4e204b99821bedcb349ed54-0
openvpn-openssl 2.4.4-1

Try as I might raising a tun iface for an ovpn outbound client is not working. A server instance is also configured and running with no issues. Shutting down the ovpn server part is not solving the matter.
There are no errors showing in the sys/kernel logs - what other places there are to troubleshoot the matter?

Have not found the root cause but made a vanilla flash with TOS 3.10 and the iface is being raised.