IPsec Site-to-Site on XG18 not working

Hi,

I installed Sophos SFOS with XG18 on my 2 SG210 Appliances, becuase we need to have more then 1 DHCP-Relay.

But even with Firewall XG the IPsec Site-to-Site won´t work.

I configured it for 3 VLANs like mentioned here:
https://docs.sophos.com/nsg/sophos-firewall/18.5/Help/en-us/webhelp/onlinehelp/AdministratorHelp/VPN/SiteToSiteVPN/VPNConfigureSiteToSiteIPsecNAT/index.html

IPsec is probably connected, but doesn´t transfer data.
Not even a Ping from one site to another is possible.
Inbound and outbound rules in firewall and also report-section don´t show transmitted data.

Do I have to do some additional NATing?

I need it to run because our backoffice is offline actually without connection to HQ.

Thanks for help