I solved it by reinstalling TwinCAT Drive Manager 2. It turned out that I recently updated to TwinCAT version 4024.32, which apparently removed some config files for 'AX8108-0110-0105'. See below the diff of the files in C:\TwinCAT\3.1\Config\Io\EtherCAT after installing 4032 and after reinstalling TwinCAT Drive Manager 2: