You can get the following message in the SonicWALL Log:
IKEv2 Initiator: Remote Party Timeout – Retransmitting IKEv2 Request
This is because you have set up a VPN on one site that is unable to connect to the other site. This may be a misconfiguration of the VPN on either site.
To fix this, disable / delete the VPN that is not connected, or fix the VPN connectivity issues.