Are you sure the MLbevelreflect.exe plugin is in the correct plugin folder ? For example, have you swapped Gimp versions from samj portable to regular gimp.org which use different folders.
This a 30 second example using Win10 / Gimp 2.10.38 / MLbevelreflect.exe V2 64bit (zipped & attached)
https://i.imgur.com/12Rkx4s.mp4
This a 30 second example using Win10 / Gimp 2.10.38 / MLbevelreflect.exe V2 64bit (zipped & attached)
https://i.imgur.com/12Rkx4s.mp4