Hi,
The last tunnel down reason is seen as follows :-
Last Tunnel Down Reason: VPN monitoring
This means that VPN monitoring is causing your tunnel to be down when it does not get a response from the other side.
You can check if we are getting proper response from the other side and if VPN monitoring is configured properly there.
Removing vpn monitoring from your tunnel configuration should take care of this issue.
Regards,
Sahil Sharma
---------------------------------------------------
Please mark my solution as accepted if it helped, Kudos are appreciated as well.