Just bringing this up to date so that perhaps it can help someone else who has a problem with Family Tree Maker at some stage.
A member on the ancestry message board said that the only way to get a response from MacKiev was to go on their Livechat. (They even said that there were scammers out there offering to fix problems on FTM for money, masquerading as software technicians.) I went on the Livechat and the "support officer", after covering a couple of possibilities, asked if it was okay if he replied by email because the problem was not something that he could fix via Livechat. It looked like it might have to be referred to an "engineer". He asked a couple of questions by email. I replied. Then I heard nothing for seven days despite my sending follow up emails. Finally he sent an email with another question. I answered that. Then there was nothing for two days. Finally I received this email:
"Hi Peter,
"My name is Linda, I am senior technical support agent at Software Mackiev.
"I am writing regarding the investigation of the issue with Family Tree Maker you provided to us.
"After investigating the problem with engineers, we have been able to reproduce it on our side. This issues is caused by compatibility conflict with Mac OS Ventrua. The new application bug has been submitted and dedicated team of engineers have been assigned to develop a fix for it as it's our top priority to make FTM 2019 compatible with all the updates Apple releases.
"As soon as there is an update available to fix this problem, we will notify you via email.
"Sorry for the inconveniences occurred and thank you very much for reporting this issue to us!
"Regards,
Linda"
My takeaway from this is that they are trying, but perhaps the knowledge/training of the support officers and the responsiveness of those up the line is bit lacking (if it was passed up the line in a timely manner). Certainly the overall response is better than some other companies I've dealt with in the past.
Peter