Like all others I used this Application for years in combination with a NAS. After the upgrade to Cataline the import process seems to perform an action, but nothing happens. So far non of the recommendations provided here solved this issue for me.
These things are really worrying ... the most important reason to pay 3x more than for a non Apple system was the stability, performance, ingenious implementations and great looks, but now in 2020 these reasons start to apply less and less ... and to be honest, I am in the middle in deciding to upgrade both my iMac and iPhone ... once no need to consider e.g. windows and android or Chinese brands, etc but hmmm, why pay too much for the same non-satisfying software?
Apple: fire some of your marketing, sales and management people, stop outsourcing to semi-slaves in cheap labour regions expecting you get the same quality, and use your endless amount of money to do something good again for your customers ... and soon.