Apex class warning error
Starting with Salesforce Winter ’19, PureCloud for Salesforce users may see warning messages indicating that they do not have access to an Apex class.
Users of current Salesforce organization can proceed without any issue. Users of new Salesforce organizations must be granted permission for each Apex class. For more information, see Apex Class access for Open CTI and Administrator requirements for the PureCloud embedded clients.
For more information about the integration, see About PureCloud for Salesforce.