Honeywell Vertex M User Manual page 258

4. On the Vertex M, open FactoryTalk Linx Gateway Configuration, if not already open. Select
Certificate Management tab, in the Rejected Certificates list, select the certificate that
appears to be from the UA client, then press Trust button. After trusting the certificate, the
certificate should be added to the Trusted Certificates list.
5. After trusting the UA client certificate on the Vertex OPC UA server, return to UA client to
attempt connecting again.
Vertex M 258 User Manual