Unfortunately, Apple has become more Microsoft-like about demanding attention on updates.
I had the same problem with a previous MacOS update as you had with Mojave, so I've made sure since then to always check the Olympus site before a system update. Olympus announced on its website (09/24/18) that DSS Player for Mac is not yet supporting Mojave: 'Therefore, we recommend not to update your MacOS until we announce the full compatibility of DSS Player for Mac.' The updated software was released in January and is available for download.
