@nocling I have not activated MOBIKE. From my point of view, this is not necessary for a site-to-site VPN connection.
Here are my P1 Settings:
Screenshot 2023-01-29 150303.png
Here are my Advanced IPsec Settings:
Screenshot 2023-01-29 150111.png
I also activated Asynchronous Cryptography, but I didn't see any advantages during testing, so I deactivated it again.
I am at a loss and do not know if the problem is due to the pfSense settings. With the Netgate 1537, do drivers for the hardware also have to be updated in addition to the pfSense? Or is this done with the installation of pfSense? System -> Netgate Firmware Upgrade shows that this function is not available for this hardware.