i use nik color efex 5.0.2 and lightroom 11.4.1 (on mac os catalina 10.15.7. macbook pro) . i use nik as external editor, after i finish processing it can take few minutes until i see the image in develop mode (see grey screen). never had this problem on other editors or other nik versions,
I'm running MacOS Monterey 12.5 but having similar problems with Nik 5 and Lightroom. Until upgrading to Nik 5 and then 5.02 I used Nik 4 for ages and had no problems. Since installing Nik 5 I have been unable to get it to cooperate with LR despite uninstalling both programs, re-installing (2 x of each) etc. Currently, Nik sends my image back to LR but many LR commands are greyed out, the LR histogram and keywords flash on and off and eventually I have to force quit LR..