The CallGraph Skype recorder is built on the Skype Desktop API. Some parts of the API was deprecated by Microsoft last year. The announcement can be found at the following link.
Fortunately CallGraph did not use those APIs and was still working. With the 18.104.22.168 Skype update however, it seems that some more APIs have been removed from Skype. We have received multiple bug reports that CallGraph has stopped working after this update. CallGraph does not seem to receive any data from Skype and therefore the other side of the call does not get recorded. But there has been no update from Microsoft regarding this.
The best advice we can give right now is to try out the other Skype recorders listed on the Skype Website. Some of them are free and still available. If the API has been deprecated, then none of the Skype recorders will work.
In the meantime, if you are facing issues with CallGraph, please enable logging, record a test call and send it to firstname.lastname@example.org. We will keep monitoring the situation and update whenever we have more information.