Opnsense immediately down ipsec tunnel.

[lncan]

Hello guys, I setup a tunnel between a remote host on google cloud and opnsense router on local network. It's success. But after working about 20-30 minutes, opnsense down ipsec tunnel. and then, I must go to VPN>IPsec>Status Overiew to start it by my self. I don't know why. Could you please tell me the detail solution to fix this error? Thanks all.