When Excalibur after an update (1.2.7 -> 1.2.9) does not respond/open/shortcuts not working - try starting premiere and holding COMM+SHIFT and delete plug-in cache. Worked for me - Excalibur (1.2.9), PP25, OSX 14.7.4, intel mac pro 2019.
Excalibur (1.2.9) not working after update mac