I have searched around but can't find any references to the problem I'm experiencing with iMessage.
I had no problem setting up my new Mojave install and getting iMessage/iCloud to work. I can send and receive iMessages without issue, however my iMessage app won't show the messages in the transcript box. They show up under the contact name, and I will receive a notification when new iMessages arrive, but can't view the conversation.
I even sent myself a photo from my iPhone and was able to click and drag it out of message transcript window in OSX (by guessing and clicking where the photo was within the transcript box), so there is something going on in there, but I am at a loss as to how this can be fixed.
Any help would be greatly appreciated!